add test explorer extension to dotnet devcontainer

dotnet/.devcontainer/devcontainer.json

@@ -3,7 +3,14 @@
 {
 	"name": "C# (.NET)",
 	// Or use a Dockerfile or Docker Compose file. More info: https://containers.dev/guide/dockerfile
-	"image": "mcr.microsoft.com/devcontainers/dotnet:0-6.0-bullseye"
+	"image": "mcr.microsoft.com/devcontainers/dotnet:0-6.0-bullseye",
+	"customizations": {
+		"vscode": {
+			"extensions": [
+				"jcamp.dotnet-test-provider-explorer"
+			]
+		}
+	}
 	// Features to add to the dev container. More info: https://containers.dev/features.
 	// "features": {},
 	// Use 'forwardPorts' to make a list of ports inside the container available locally.