Add types to nextConfig in default template

[mohsen1]

Enable editors to suggest properties for the config object. Also let TypeScript check for type errors in the configuration when using TypeScript

[ijjk]

Adding the type reference to the default template looks good, I don't think we want to add the @ts-check by default to allow users to add it if desired. Thanks for the PR!

[ijjk]

Stats from current PR

Default Build (Decrease detected ✓)

General Overall increase ⚠️

	vercel/next.js canary	mohsen1/next.js add-ts-check-and-types-to-next-config	Change
buildDuration	15.3s	15.5s	⚠️ +137ms
buildDurationCached	6.1s	6.1s	-32ms
nodeModulesSize	359 MB	359 MB	⚠️ +1 B

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	mohsen1/next.js add-ts-check-and-types-to-next-config	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.22	3.204	-0.02
/ avg req/sec	776.29	780.33	+4.04
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.363	1.369	⚠️ +0.01
/error-in-render avg req/sec	1833.76	1826.77	⚠️ -6.99

Client Bundles (main, webpack, commons)

	vercel/next.js canary	mohsen1/next.js add-ts-check-and-types-to-next-config	Change
450.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.2 kB	42.2 kB	✓
main-HASH.js gzip	27.4 kB	27.4 kB	✓
webpack-HASH.js gzip	1.44 kB	1.44 kB	✓
Overall change	71.2 kB	71.2 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	mohsen1/next.js add-ts-check-and-types-to-next-config	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	mohsen1/next.js add-ts-check-and-types-to-next-config	Change
_app-HASH.js gzip	1.36 kB	1.36 kB	✓
_error-HASH.js gzip	194 B	194 B	✓
amp-HASH.js gzip	312 B	312 B	✓
css-HASH.js gzip	326 B	326 B	✓
dynamic-HASH.js gzip	2.37 kB	2.37 kB	✓
head-HASH.js gzip	350 B	350 B	✓
hooks-HASH.js gzip	919 B	919 B	✓
image-HASH.js gzip	4.94 kB	4.94 kB	✓
index-HASH.js gzip	263 B	263 B	✓
link-HASH.js gzip	2.19 kB	2.19 kB	✓
routerDirect..HASH.js gzip	321 B	321 B	✓
script-HASH.js gzip	383 B	383 B	✓
withRouter-HASH.js gzip	318 B	318 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	14.3 kB	14.3 kB	✓

Client Build Manifests

	vercel/next.js canary	mohsen1/next.js add-ts-check-and-types-to-next-config	Change
_buildManifest.js gzip	459 B	459 B	✓
Overall change	459 B	459 B	✓

Rendered Page Sizes

	vercel/next.js canary	mohsen1/next.js add-ts-check-and-types-to-next-config	Change
index.html gzip	532 B	532 B	✓
link.html gzip	546 B	546 B	✓
withRouter.html gzip	526 B	526 B	✓
Overall change	1.6 kB	1.6 kB	✓

---

Default Build with SWC (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	mohsen1/next.js add-ts-check-and-types-to-next-config	Change
buildDuration	19.1s	19.2s	⚠️ +50ms
buildDurationCached	6s	6s	⚠️ +40ms
nodeModulesSize	359 MB	359 MB	⚠️ +1 B

Page Load Tests Overall increase ✓

	vercel/next.js canary	mohsen1/next.js add-ts-check-and-types-to-next-config	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.198	3.199	0
/ avg req/sec	781.64	781.49	⚠️ -0.15
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.386	1.347	-0.04
/error-in-render avg req/sec	1803.43	1856.04	+52.61

Client Bundles (main, webpack, commons)

	vercel/next.js canary	mohsen1/next.js add-ts-check-and-types-to-next-config	Change
450.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.3 kB	42.3 kB	✓
main-HASH.js gzip	27.4 kB	27.4 kB	✓
webpack-HASH.js gzip	1.44 kB	1.44 kB	✓
Overall change	71.3 kB	71.3 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	mohsen1/next.js add-ts-check-and-types-to-next-config	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	mohsen1/next.js add-ts-check-and-types-to-next-config	Change
_app-HASH.js gzip	1.35 kB	1.35 kB	✓
_error-HASH.js gzip	180 B	180 B	✓
amp-HASH.js gzip	305 B	305 B	✓
css-HASH.js gzip	321 B	321 B	✓
dynamic-HASH.js gzip	2.36 kB	2.36 kB	✓
head-HASH.js gzip	342 B	342 B	✓
hooks-HASH.js gzip	911 B	911 B	✓
image-HASH.js gzip	4.97 kB	4.97 kB	✓
index-HASH.js gzip	256 B	256 B	✓
link-HASH.js gzip	2.21 kB	2.21 kB	✓
routerDirect..HASH.js gzip	314 B	314 B	✓
script-HASH.js gzip	375 B	375 B	✓
withRouter-HASH.js gzip	309 B	309 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	14.3 kB	14.3 kB	✓

Client Build Manifests

	vercel/next.js canary	mohsen1/next.js add-ts-check-and-types-to-next-config	Change
_buildManifest.js gzip	459 B	459 B	✓
Overall change	459 B	459 B	✓

Rendered Page Sizes

	vercel/next.js canary	mohsen1/next.js add-ts-check-and-types-to-next-config	Change
index.html gzip	533 B	533 B	✓
link.html gzip	546 B	546 B	✓
withRouter.html gzip	528 B	528 B	✓
Overall change	1.61 kB	1.61 kB	✓

Commit: 4151283