Fix for #375 to add devcontainer/extensions files

.github/workflows/dotnetcore.yml

@@ -8,11 +8,11 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
     - name: Setup .NET Core
       uses: actions/setup-dotnet@v1
       with:
-        dotnet-version: 3.1.100
+        dotnet-version: 3.1.201
     - name: Build with dotnet
       run: dotnet build ./eShopOnWeb.sln --configuration Release
     - name: Test with dotnet