ci(gh-actions): add .NET 6.0 SDK

Author: nogic1008

.github/workflows/dotnet.yml

@@ -36,7 +36,10 @@ jobs:
       - name: Setup .NET SDK
         uses: actions/[email protected]
         with:
-          dotnet-version: ${{ vars.DOTNET_SDK_VERSIONS }}
+          # TODO: Remove 6.x and add to vars.DOTNET_SDK_VERSIONS
+          dotnet-version: |
+            ${{ vars.DOTNET_SDK_VERSIONS }}
+            6.x
           cache: true
           cache-dependency-path: '**/packages.lock.json'
 
@@ -58,7 +61,10 @@ jobs:
       - name: Setup .NET SDK
         uses: actions/[email protected]
         with:
-          dotnet-version: ${{ vars.DOTNET_SDK_VERSIONS }}
+          # TODO: Remove 6.x and add to vars.DOTNET_SDK_VERSIONS
+          dotnet-version: |
+            ${{ vars.DOTNET_SDK_VERSIONS }}
+            6.x
           cache: true
           cache-dependency-path: '**/packages.lock.json'