try to add more platforms to the buildx container

Author: baronfel

.github/workflows/dotnet.yml

@@ -26,6 +26,10 @@ jobs:
         global-json-file: 'global.json' # in addition to the 6.0 we need for tests, install "latest"
     - name: Build
       run: dotnet build --consoleloggerparameters:NoSummary --warnAsError
+    - name: Set up Docker Buildx to handle more platforms
+      uses: docker/setup-buildx-action@v2
+      with:
+        platforms: linux/amd64,linux/arm64,linux/386,linux/arm/v7,linux/arm/v6
     - name: Discover docker platforms
       run: docker buildx ls
     - name: Test