Example: Treat "mockServiceWorker" as a generated artifact in "with-m…

…sw" (vercel#25515)

## Changes

- Removes `mockServiceWorker.js` file and ignores it from Git. New versions of `msw` generate the worker script automatically at the location specified in `packageJson.msw.workerDirectory`. This keeps the worker script up-to-date with the currently installed version of `msw`.
- Updates `msw` package to the latest version for new features and stability improvements.

## Documentation / Examples

- [ ] Make sure the linting passes

examples/with-msw/.gitignore

@@ -7,6 +7,7 @@
 
 # testing
 /coverage
+public/mockServiceWorker.js
 
 # next.js
 /.next/

examples/with-msw/package.json

@@ -8,9 +8,12 @@
   },
   "license": "MIT",
   "dependencies": {
-    "msw": "^0.24.2",
+    "msw": "^0.29.0",
     "next": "latest",
     "react": "^17.0.1",
     "react-dom": "^17.0.1"
+  },
+  "msw": {
+    "workerDirectory": "public"
   }
 }