Add ".NET Attach" launch config

This helps debugging the source gnerator.

.vscode/launch.json

@@ -11,6 +11,11 @@
       "cwd": "${workspaceFolder}/src/Immersion",
       "console": "internalConsole",
       "stopAtEntry": false
+    },
+    {
+      "name": ".NET Attach",
+      "type": "coreclr",
+      "request": "attach"
     }
   ]
 }