[material-ui] Update TypeScript supports in v6

[oliviertassinari]

Summary

We likely can increase the minimum version of TypeScript supported: https://mui.com/material-ui/getting-started/supported-platforms/#typescript. I don't know about how much but likely some level.

Related issue with TypeScript support (which could indicate how far down we need to support TypeScript in terms of versions)

• [Box] Fix usage of not supported features in TypeScript 3.5 #35877
• [Dropdown] Fix imports of types #38296 (comment)

Examples

No response

Motivation

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Search keywords: TypeScript minimum version

[oliviertassinari]

Base UI is in theory not allowed to do this in its latest version: https://github.com/mui/base-ui/blob/4a4ccebd750dea6252cfdc07c55eb4ea474eaebe/packages/mui-base/src/index.ts#L16 cc @atomiks for context (Base UI version range can only be wider than Material UI since it's a dependency)

It breaks https://mui.com/material-ui/getting-started/supported-platforms/#typescript because this was only added in v4.5: https://www.typescriptlang.org/docs/handbook/release-notes/typescript-4-5.html#type-modifiers-on-import-names.

So 👍 on my end to at the very least bump TypeScrpt min version support from v3.5 to v3.8 to get access to https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-8.html. It's actually already broken today in Material UI and I didn't see issues about it.

Also worth looking at: https://tools-public.mui.com/prod/pages/npmVersion?package=typescript. It looks like we could bump this to at least v4.0:

Should we maybe go to v4.5 to get import { type Foo }? I don't know. It's already old: https://devblogs.microsoft.com/typescript/announcing-typescript-4-5/. So maybe we could say:

3.8 was released February 20th, 2020. Material UI v5 was released Sep 16, 2021. We could hence pick the TypeScript version that is 18 months old: TypeScript 4.9.

If we instead uses https://github.com/DefinitelyTyped/DefinitelyTyped?tab=readme-ov-file#support-window

we would then go with v4.8. I guess it's the simplest we can do? What we already say we do in the docs:

Material UI requires a minimum version of TypeScript 3.5. This aims to match the policy of DefinitelyTyped, with the support of the versions of TypeScript that are less than two years old.