Fix for #375 to add devcontainer/extensions files

.devcontainer/devcontainer.json

@@ -0,0 +1,9 @@
+{  
+    "extensions": [
+        "ms-vscode.csharp",
+        "formulahendry.dotnet-test-explorer",
+        "ms-vscode.vscode-node-azure-pack",
+        "ms-kubernetes-tools.vscode-kubernetes-tools",
+        "redhat.vscode-yaml"
+    ]
+  }