build exe (portable zip) via github workflow

.github/workflows/dotnet-desktop.yml

@@ -0,0 +1,38 @@
+name: Build and Attach to Release
+
+on:
+  release:
+    types:
+      - created
+
+jobs:
+  build:
+    permissions: write-all
+    runs-on: windows-latest
+
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v2
+
+    - name: Set up MSBuild
+      uses: microsoft/setup-msbuild@v1
+      with:
+        msbuild-version: '16.0'
+
+    - name: Restore NuGet packages
+      run: nuget restore p2pconn.sln
+
+    - name: Build
+      run: msbuild p2pconn.sln /p:Configuration=Release
+
+    - name: Zip files in p2pconn/bin/Release
+      run: |
+        Compress-Archive -Path ./p2pconn/bin/Release/* -DestinationPath ./p2pconn/bin/Release/p2p-portable.zip
+
+    - name: List contents of p2pconn/bin/Release
+      run: ls -R ./p2pconn/bin/Release
+
+    - name: Release
+      uses: softprops/action-gh-release@v1
+      with:
+        files: p2pconn/bin/Release/p2p-portable.zip