Added action.yml file tp publish action

As mentioned here https://docs.github.com/en/actions/creating-actions/publishing-actions-in-github-marketplace

action.yml

@@ -0,0 +1,112 @@
+name: CI on Push and Pull Request
+
+on: [push, pull_request]
+
+jobs:
+  Practice:
+
+    runs-on: macos-latest
+
+    steps:
+    - uses: actions/checkout@v1
+    - name: Run a one-line script
+      run: echo Hello, world!
+    - name: Run a multi-line script
+      run: |
+        echo Add other actions to build,
+        echo test, and deploy your project.
+    - name: Show what in there
+      run: |
+        ls
+    - name: Show what is inside
+      run: |
+        cd ..
+        ls
+        
+  Android:
+
+    runs-on: macos-latest
+
+    steps:
+
+    - uses: actions/checkout@v1
+
+    - name: Android
+      run: |
+        cd Blank
+        nuget restore
+        cd Blank.Android
+        msbuild Blank.Android.csproj /verbosity:normal /t:Rebuild /t:PackageForAndroid /t:SignAndroidPackage /p:Configuration=Debug 
+
+    - uses: actions/upload-artifact@v2
+      with:
+        name: Android App
+        path: Blank/Blank.Android/bin/Debug/com.tfp.blank-Signed.apk
+
+  iOS_Simulator:
+
+    runs-on: macos-latest
+
+    steps:
+
+    - name: Checkout repository
+      uses: actions/checkout@v2
+
+    - name: iOS Simulator
+      run: |
+        cd Blank
+        nuget restore
+        msbuild Blank.iOS/Blank.iOS.csproj /verbosity:normal /t:Rebuild /p:Platform=iPhoneSimulator /p:Configuration=Debug
+        
+    - uses: actions/upload-artifact@v2
+      with:
+        name: iOS Simulator App
+        path: Blank/Blank.iOS/bin/iPhoneSimulator/Debug/Blank.iOS.app
+
+  iOS_Device:
+
+    runs-on: macos-latest
+
+    steps:
+
+    - name: Checkout repository
+      uses: actions/checkout@v2
+    - name: Install the Apple certificate and provisioning profile
+      env:
+        BUILD_CERTIFICATE_BASE64: ${{ secrets.BUILD_CERTIFICATE_BASE64 }}
+        P12_PASSWORD: ${{ secrets.P12_PASSWORD }}
+        BUILD_PROVISION_PROFILE_BASE64: ${{ secrets.BUILD_PROVISION_PROFILE_BASE64 }}
+        KEYCHAIN_PASSWORD: ${{ secrets.KEYCHAIN_PASSWORD }}
+      run: |
+        # create variables
+        CERTIFICATE_PATH=$RUNNER_TEMP/build_certificate.p12
+        PP_PATH=$RUNNER_TEMP/build_pp.mobileprovision
+        KEYCHAIN_PATH=$RUNNER_TEMP/app-signing.keychain-db
+
+        # import certificate and provisioning profile from secrets
+        echo -n "$BUILD_CERTIFICATE_BASE64" | base64 --decode --output $CERTIFICATE_PATH
+        echo -n "$BUILD_PROVISION_PROFILE_BASE64" | base64 --decode --output $PP_PATH
+
+        # create temporary keychain
+        security create-keychain -p $KEYCHAIN_PASSWORD $KEYCHAIN_PATH
+        security set-keychain-settings -lut 21600 $KEYCHAIN_PATH
+        security unlock-keychain -p $KEYCHAIN_PASSWORD $KEYCHAIN_PATH
+
+        # import certificate to keychain
+        security import $CERTIFICATE_PATH -P $P12_PASSWORD -A -t cert -f pkcs12 -k $KEYCHAIN_PATH
+        security list-keychain -d user -s $KEYCHAIN_PATH
+
+        # apply provisioning profile
+        mkdir -p ~/Library/MobileDevice/Provisioning\ Profiles
+        cp $PP_PATH ~/Library/MobileDevice/Provisioning\ Profiles   
+        
+    - name: iOS Device
+      run: |
+        cd Blank
+        nuget restore
+        msbuild Blank.iOS/Blank.iOS.csproj /verbosity:normal /t:Rebuild /p:Platform=iPhone /p:Configuration=Debug
+
+    - uses: actions/upload-artifact@v2
+      with:
+        name: iOS Device App
+        path: Blank/Blank.iOS/bin/iPhone/Debug/Blank.iOS.app