Add Debug Welcome View (dotnet#4797)

* Add Debug Welcome View

This PR adds a welcome view when the debug language detected is C#.

* Use aka.ms link

Author: WardenGnaw

package.json

@@ -3741,6 +3741,13 @@
           "group": "2_dotnet@2"
         }
       ]
-    }
+    },
+    "viewsWelcome": [
+      {
+        "view": "debug",
+        "contents": "[Generate C# Assets for Build and Debug](command:dotnet.generateAssets)\n\nTo learn more about launch.json, see [Configuring launch.json for C# debugging](https://aka.ms/VSCode-CS-LaunchJson).",
+        "when": "debugStartLanguage == csharp"
+      }
+    ]
   }
 }