create sample specifically for multi-arch-manifest flows

.github/workflows/multi-arch-sample.yml

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+name: multi-arch image sample
+
+on:
+  push:
+  workflow_dispatch:
+
+env:
+  GITHUB_USERNAME: baronfel
+  APP_NAME: multi-arch-sample
+
+jobs:
+  create-multiarch-image:
+    permissions:
+      contents: read
+      packages: write
+    runs-on: ubuntu-latest
+    steps:
+    - name: Login to ghcr.io
+      uses: docker/login-action@v3
+      with:
+        registry: ghcr.io
+        username: ${{ github.actor }}
+        password: ${{ secrets.GITHUB_TOKEN }}
+    - name: Get the code
+      uses: actions/checkout@v2
+    - name: build the x64 image
+      id: build-x64
+      working-directory: src/multi-arch-sample
+      run: |
+        dotnet publish -t:PublishContainer --arch x64 -p ContainerImageLabel=latest-x64 -p ContainerRepository=ghcr.io/${{github.repository_owner}}/${{env.APP_NAME}}
+        echo "generated_container_name=ghcr.io/${{github.repository_owner}}/${{env.APP_NAME}}:latest-x64" >> $GITHUB_OUTPUT
+    - name: build the arm64 image
+      id: build-arm64
+      run: |
+        dotnet publish -t:PublishContainer --arch arm64 -p ContainerImageLabel=latest-arm64 -p ContainerRepository=ghcr.io/${{github.repository_owner}}/${{env.APP_NAME}}
+        echo "generated_container_name=ghcr.io/${{github.repository_owner}}/${{env.APP_NAME}}:latest-arm64" >> $GITHUB_OUTPUT
+    - name: create the multi-image manifest
+      run: |
+        docker manifest create ghcr.io/${{github.repository_owner}}/${{env.APP_NAME}}:latest \
+          ${{ steps.build-x64.outputs.generated_container_name }} \
+          ${{ steps.build-arm64.outputs.generated_container_name }} \
+          
+        docker manifest push ghcr.io/${{github.repository_owner}}/${{env.APP_NAME}}:latest

src/multi-arch-sample/Program.cs

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+Console.WriteLine($"Hello, World from {System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription} on {System.Runtime.InteropServices.RuntimeInformation.OSDescription} with {System.Runtime.InteropServices.RuntimeInformation.ProcessArchitecture} chips!");

src/multi-arch-sample/multi-arch-sample.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net9.0</TargetFramework>
+    <RootNamespace>multi_arch_sample</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <EnableSdkContainerSupport>true</EnableSdkContainerSupport>
+  </PropertyGroup>
+
+</Project>