feat: add wasm demo using podman

Use ubi image, podman and ascii art from podman

Include CI using podman to build the image as well

.github/workflows/build-publish-wasm.yaml

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+---
+#
+# Copyright (C) 2023 Red Hat, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+name: Build and publish the wasm examples
+
+on:
+  push:
+    paths:
+      - "wasm/**"
+      - ".github/workflows/build-publish-wasm.yaml"
+  workflow_dispatch:
+
+jobs:
+  build:
+    name: Build all wasm examples
+    runs-on: ubuntu-22.04
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install qemu dependency
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y qemu-user-static
+
+      - name: Update podman
+        run: |
+          sudo sh -c "echo 'deb https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/unstable/xUbuntu_22.04/ /' > /etc/apt/sources.list.d/devel:kubic:libcontainers:unstable.list"
+          curl -L https://build.opensuse.org/projects/devel:kubic:libcontainers:unstable/signing_keys/download?kind=gpg | sudo apt-key add -
+          sudo apt-get update -qq
+          sudo apt-get install -y podman
+          podman version
+
+      - name: Build Rust Hello World Wasm Image
+        id: build-image
+        run: |
+          SHORT_SHA1=$(echo ${GITHUB_SHA} | cut -c1-7)
+          podman build --platform wasi/wasm -t wasm-rust-hello-world -f ./wasm/rust-hello-world/Containerfile ./wasm/rust-hello-world
+          podman tag wasm-rust-hello-world wasm-rust-hello-world:${SHORT_SHA1}
+          echo "tags=latest ${SHORT_SHA1}" >> $GITHUB_OUTPUT
+
+      - name: Log in to Red Hat Registry
+        uses: redhat-actions/podman-login@v1
+        with:
+          registry: quay.io
+          username: ${{ secrets.QUAY_USERNAME }}
+          password: ${{ secrets.QUAY_PASSWORD }}
+
+      - name: list images
+        run: |
+          podman images
+          echo "the tags are ${{ steps.build-image.outputs.tags }}"
+
+      - name: Push To quay.io
+        id: push-to-quay
+        uses: redhat-actions/push-to-registry@v2
+        with:
+          image: wasm-rust-hello-world
+          tags: ${{ steps.build-image.outputs.tags }}
+          registry: quay.io/podman-desktop-demo

wasm/rust-hello-world/Cargo.toml

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+#
+# Copyright (C) 2023 Red Hat, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+[package]
+name = "rust-hello-world"
+version = "0.1.0"
+edition = "2021"
+
+[[bin]]
+name = "rust-hello"
+path = "src/main.rs"

wasm/rust-hello-world/Containerfile

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+#
+# Copyright (C) 2023 Red Hat, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+# Build using the host platform (and not target platform wasi/wasm)
+FROM --platform=$BUILDPLATFORM docker.io/redhat/ubi9-minimal as builder
+
+# install rust and wasm/wasi target
+RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y \
+    && source "$HOME/.cargo/env" && rustup target add wasm32-wasi
+
+# copy source code
+COPY Cargo.toml /app/
+COPY src /app/src 
+
+# change working directory
+WORKDIR /app
+
+# Build
+RUN source "$HOME/.cargo/env" && cd /app && cargo build --target wasm32-wasi --release
+
+# now copy the wasm binary and flag it as the entrypoint
+FROM scratch
+ENTRYPOINT [ "/rust-hello-world.wasm" ]
+COPY --from=builder /app/target/wasm32-wasi/release/rust-hello.wasm /rust-hello-world.wasm

wasm/rust-hello-world/README.md

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+# Hello world in Rust
+
+Inspired from https://doc.rust-lang.org/rust-by-example/hello.html
+and the C podman hello https://github.com/containers/PodmanHello/blob/main/podman_hello_world.c
+
+It's displaying a Hello World with some ascii art from Máirín Duffy @mairin
+
+In the Containerfile, we build using wasm32-wasi and the target platform of the image is `wasi/wasm`
+Then the .wasm binary is copied in a scratch image with architecture `wasi/wasm`
+
+
+
+## Build command:
+
+### prerequisites
+
+- A recent podman version (not the v3.x for example on Ubuntu LTS)
+
+
+### instructions
+
+podman build --platform=wasi/wasm  -t wasm-rust-hello-world .
+
+
+## Run command
+
+### prerequisites
+
+crun-wasm/wasmedge-rt packages need to be installed in the podman machine/host
+
+# on Windows, this is the default now
+# on macOS: need to initialize a podman machine using next channel
+
+
+### running from the previous build step
+
+podman run wasm-rust-hello-world
+
+### running from quay.io image
+
+podman run --platform wasi/wasm quay.io/podman-desktop-demo/wasm-rust-hello-world

wasm/rust-hello-world/src/main.rs

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+/**********************************************************************
+ * Copyright (C) 2023 Red Hat, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ ***********************************************************************/
+
+fn main() {
+
+    // use of strings literal for multi-line string
+    // https://doc.rust-lang.org/reference/tokens.html#raw-string-literals
+
+    // ascii art from Máirín Duffy @mairin
+    let hello = r#"
+!... Hello Podman wasm World ...!
+
+         .--"--.
+       / -     - \
+      / (O)   (O) \
+   ~~~| -=(,Y,)=- |
+    .---. /`  \   |~~
+ ~/  o  o \~~~~.----. ~~
+  | =(X)= |~  / (O (O) \
+   ~~~~~~~  ~| =(Y_)=-  |
+  ~~~~    ~~~|   U      |~~
+
+Project:   https://github.com/containers/podman
+Website:   https://podman.io
+Documents: https://docs.podman.io
+Twitter:   @Podman_io
+"#;
+    println!("{}", hello);
+
+  }
+