[Docs] Update custom server docs

[lfades]

[ch3235]

[ijjk]

Stats from current PR

Default Server Mode (Decrease detected ✓)

General

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
buildDuration	11.7s	12.4s	⚠️ +637ms
nodeModulesSize	65.2 MB	65.2 MB	✓

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.076	2.225	⚠️ +0.15
/ avg req/sec	1204.01	1123.4	-80.61
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.45	1.393	-0.06
/error-in-render avg req/sec	1724.64	1794.57	⚠️ +69.93

Client Bundles (main, webpack, commons)

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
main-HASH.js gzip	6.51 kB	6.51 kB	✓
webpack-HASH.js gzip	746 B	746 B	✓
de003c3a9d30..0538.js gzip	10.5 kB	10.5 kB	✓
framework.HASH.js gzip	39.1 kB	39.1 kB	✓
Overall change	56.9 kB	56.9 kB	✓

Client Bundles (main, webpack, commons) Modern

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
main-HASH.module.js gzip	5.6 kB	5.6 kB	✓
webpack-HASH..dule.js gzip	746 B	746 B	✓
de003c3a9d30..dule.js gzip	6.93 kB	6.93 kB	✓
framework.HA..dule.js gzip	39.1 kB	39.1 kB	✓
Overall change	52.4 kB	52.4 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
polyfills-HASH.js gzip	26.3 kB	26.3 kB	✓
Overall change	26.3 kB	26.3 kB	✓

Client Pages

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
routerDirect.js gzip	279 B	279 B	✓
withRouter.js gzip	278 B	278 B	✓
_error.js gzip	3.37 kB	3.37 kB	✓
index.js gzip	222 B	222 B	✓
link.js gzip	2.05 kB	2.05 kB	✓
hooks.js gzip	881 B	881 B	✓
_app.js gzip	1.26 kB	1.26 kB	✓
Overall change	8.34 kB	8.34 kB	✓

Client Pages Modern

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
index.module.js gzip	223 B	223 B	✓
routerDirect..dule.js gzip	281 B	281 B	✓
withRouter.m..dule.js gzip	278 B	278 B	✓
hooks.module.js gzip	383 B	383 B	✓
_error.module.js gzip	2.21 kB	2.21 kB	✓
link.module.js gzip	1.52 kB	1.52 kB	✓
_app.module.js gzip	604 B	604 B	✓
Overall change	5.49 kB	5.49 kB	✓

Client Build Manifests

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
_buildManifest.js gzip	270 B	270 B	✓
_buildManife..dule.js gzip	274 B	274 B	✓
Overall change	544 B	544 B	✓

Rendered Page Sizes

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
index.html gzip	956 B	956 B	✓
link.html gzip	963 B	963 B	✓
withRouter.html gzip	949 B	949 B	✓
Overall change	2.87 kB	2.87 kB	✓

---

Serverless Mode

General

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
buildDuration	13s	12.9s	-25ms
nodeModulesSize	65.2 MB	65.2 MB	✓

Client Bundles (main, webpack, commons)

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
main-HASH.js gzip	6.51 kB	6.51 kB	✓
webpack-HASH.js gzip	746 B	746 B	✓
de003c3a9d30..0538.js gzip	10.5 kB	10.5 kB	✓
framework.HASH.js gzip	39.1 kB	39.1 kB	✓
Overall change	56.9 kB	56.9 kB	✓

Client Bundles (main, webpack, commons) Modern

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
main-HASH.module.js gzip	5.6 kB	5.6 kB	✓
webpack-HASH..dule.js gzip	746 B	746 B	✓
de003c3a9d30..dule.js gzip	6.93 kB	6.93 kB	✓
framework.HA..dule.js gzip	39.1 kB	39.1 kB	✓
Overall change	52.4 kB	52.4 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
polyfills-HASH.js gzip	26.3 kB	26.3 kB	✓
Overall change	26.3 kB	26.3 kB	✓

Client Pages

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
routerDirect.js gzip	279 B	279 B	✓
withRouter.js gzip	278 B	278 B	✓
_error.js gzip	3.37 kB	3.37 kB	✓
index.js gzip	222 B	222 B	✓
link.js gzip	2.05 kB	2.05 kB	✓
hooks.js gzip	881 B	881 B	✓
_app.js gzip	1.26 kB	1.26 kB	✓
Overall change	8.34 kB	8.34 kB	✓

Client Pages Modern

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
index.module.js gzip	223 B	223 B	✓
routerDirect..dule.js gzip	281 B	281 B	✓
withRouter.m..dule.js gzip	278 B	278 B	✓
hooks.module.js gzip	383 B	383 B	✓
_error.module.js gzip	2.21 kB	2.21 kB	✓
link.module.js gzip	1.52 kB	1.52 kB	✓
_app.module.js gzip	604 B	604 B	✓
Overall change	5.49 kB	5.49 kB	✓

Client Build Manifests

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
_buildManifest.js gzip	270 B	270 B	✓
_buildManife..dule.js gzip	274 B	274 B	✓
Overall change	544 B	544 B	✓

Serverless bundles

	vercel/next.js canary	lfades/next.js chore/custom-server-docs	Change
_error.js	875 kB	875 kB	✓
404.html	4.17 kB	4.17 kB	✓
hooks.html	3.79 kB	3.79 kB	✓
index.js	875 kB	875 kB	✓
link.js	913 kB	913 kB	✓
routerDirect.js	905 kB	905 kB	✓
withRouter.js	905 kB	905 kB	✓
Overall change	4.48 MB	4.48 MB	✓