docs: point out symlink issues and solution on Windows (#7465)

CONTRIBUTING.md

@@ -69,7 +69,9 @@ And re-run `pnpm install` to link the package.
 
 Each package under `packages/playground/` contains a `__tests__` directory. The tests are run using [Jest](https://jestjs.io/) + [Playwright](https://playwright.dev/) with custom integrations to make writing tests simple. The detailed setup is inside `jest.config.js` and `scripts/jest*` files.
 
-Each test can be run under either dev server mode or build mode. Make sure that [Vite has been built](#repo-setup).
+Before running the tests, make sure that [Vite has been built](#repo-setup). On Windows, you may want to [activate Developer Mode](https://docs.microsoft.com/en-us/windows/apps/get-started/enable-your-device-for-development) to solve [issues with symlink creation for non-admins](https://github.com/vitejs/vite/issues/7390).
+
+Each test can be run under either dev server mode or build mode.
 
 - `pnpm test` by default runs every test in both serve and build mode.