Add cross-env to ensure examples work on Windows 10

[awareness481]

Closes #16693

[ijjk]

Stats from current PR

Default Server Mode (Decrease detected ✓)

General

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
buildDuration	12.3s	13s	⚠️ +724ms
nodeModulesSize	57.4 MB	57.4 MB	✓

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.403	2.467	⚠️ +0.06
/ avg req/sec	1040.46	1013.33	⚠️ -27.13
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.44	1.503	⚠️ +0.06
/error-in-render avg req/sec	1735.86	1663.65	⚠️ -72.21

Client Bundles (main, webpack, commons)

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
677f882d2ed8..f20b.js gzip	10.3 kB	10.3 kB	✓
framework.HASH.js gzip	39 kB	39 kB	✓
main-49b1fd5..c64c.js gzip	7.35 kB	7.35 kB	✓
webpack-e067..f178.js gzip	751 B	751 B	✓
Overall change	57.3 kB	57.3 kB	✓

Client Bundles (main, webpack, commons) Modern

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
677f882d2ed8..dule.js gzip	6.13 kB	6.13 kB	✓
framework.HA..dule.js gzip	39 kB	39 kB	✓
main-99715b4..dule.js gzip	6.4 kB	6.4 kB	✓
webpack-07c5..dule.js gzip	751 B	751 B	✓
Overall change	52.2 kB	52.2 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
polyfills-4b..e242.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
_app-9a0b9e1..b37e.js gzip	1.28 kB	1.28 kB	✓
_error-28298..e0c9.js gzip	3.44 kB	3.44 kB	✓
hooks-89731c..c609.js gzip	887 B	887 B	✓
index-17468f..5d83.js gzip	227 B	227 B	✓
link-000f151..65d4.js gzip	1.29 kB	1.29 kB	✓
routerDirect..924c.js gzip	284 B	284 B	✓
withRouter-7..c13d.js gzip	284 B	284 B	✓
Overall change	7.69 kB	7.69 kB	✓

Client Pages Modern

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
_app-75d3a82..dule.js gzip	625 B	625 B	✓
_error-65c8a..dule.js gzip	2.29 kB	2.29 kB	✓
hooks-cbf13f..dule.js gzip	387 B	387 B	✓
index-b9a643..dule.js gzip	226 B	226 B	✓
link-4cfda7a..dule.js gzip	1.26 kB	1.26 kB	✓
routerDirect..dule.js gzip	284 B	284 B	✓
withRouter-f..dule.js gzip	282 B	282 B	✓
Overall change	5.35 kB	5.35 kB	✓

Client Build Manifests

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
_buildManifest.js gzip	322 B	322 B	✓
_buildManife..dule.js gzip	330 B	330 B	✓
Overall change	652 B	652 B	✓

Rendered Page Sizes

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
index.html gzip	971 B	971 B	✓
link.html gzip	977 B	977 B	✓
withRouter.html gzip	964 B	964 B	✓
Overall change	2.91 kB	2.91 kB	✓

---

Serverless Mode

General

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
buildDuration	13.4s	13.6s	⚠️ +132ms
nodeModulesSize	57.4 MB	57.4 MB	✓

Client Bundles (main, webpack, commons)

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
677f882d2ed8..f20b.js gzip	10.3 kB	10.3 kB	✓
framework.HASH.js gzip	39 kB	39 kB	✓
main-49b1fd5..c64c.js gzip	7.35 kB	7.35 kB	✓
webpack-e067..f178.js gzip	751 B	751 B	✓
Overall change	57.3 kB	57.3 kB	✓

Client Bundles (main, webpack, commons) Modern

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
677f882d2ed8..dule.js gzip	6.13 kB	6.13 kB	✓
framework.HA..dule.js gzip	39 kB	39 kB	✓
main-99715b4..dule.js gzip	6.4 kB	6.4 kB	✓
webpack-07c5..dule.js gzip	751 B	751 B	✓
Overall change	52.2 kB	52.2 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
polyfills-4b..e242.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
_app-9a0b9e1..b37e.js gzip	1.28 kB	1.28 kB	✓
_error-28298..e0c9.js gzip	3.44 kB	3.44 kB	✓
hooks-89731c..c609.js gzip	887 B	887 B	✓
index-17468f..5d83.js gzip	227 B	227 B	✓
link-000f151..65d4.js gzip	1.29 kB	1.29 kB	✓
routerDirect..924c.js gzip	284 B	284 B	✓
withRouter-7..c13d.js gzip	284 B	284 B	✓
Overall change	7.69 kB	7.69 kB	✓

Client Pages Modern

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
_app-75d3a82..dule.js gzip	625 B	625 B	✓
_error-65c8a..dule.js gzip	2.29 kB	2.29 kB	✓
hooks-cbf13f..dule.js gzip	387 B	387 B	✓
index-b9a643..dule.js gzip	226 B	226 B	✓
link-4cfda7a..dule.js gzip	1.26 kB	1.26 kB	✓
routerDirect..dule.js gzip	284 B	284 B	✓
withRouter-f..dule.js gzip	282 B	282 B	✓
Overall change	5.35 kB	5.35 kB	✓

Client Build Manifests

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
_buildManifest.js gzip	322 B	322 B	✓
_buildManife..dule.js gzip	330 B	330 B	✓
Overall change	652 B	652 B	✓

Serverless bundles

	vercel/next.js canary	awareness481/next.js with-cross-env	Change
_error.js	1.03 MB	1.03 MB	✓
404.html	4.22 kB	4.22 kB	✓
hooks.html	3.86 kB	3.86 kB	✓
index.js	1.03 MB	1.03 MB	✓
link.js	1.07 MB	1.07 MB	✓
routerDirect.js	1.07 MB	1.07 MB	✓
withRouter.js	1.07 MB	1.07 MB	✓
Overall change	5.28 MB	5.28 MB	✓

Commit: 85ddbaa

[Timer]

LGTM thanks!