[next] Deprecating DefinitelyTyped types for next

[resir014]

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• I tried using the @types/next package and had problems.
• I tried using the latest stable version of tsc. https://www.npmjs.com/package/typescript
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• Mention the authors (see Definitions by: in index.d.ts) so they can respond.
  • Authors: @Dru89 @brikou @jthegedus @scottdj92 @joaovieira @ajliv

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---

So Next.js 9 is released, and since they have migrated their core codebase to TypeScript, they have now also shipped built-in typings as of this version. So as of next@9.0.0, we will no longer have to install @types/next.

So from now on, the course of actions to take will be as follows:

• Merge in maintenance fixes into @types/next@8 when necessary.
• Deprecate the DefinitelyTyped typings, which will close this issue (follow these instructions)
• Further updates/fixes to the typings shall be made to the upstream Next.js repo

@Dru89 @brikou @jthegedus @scottdj92 @joaovieira @ajliv Our work here is done! 🎉