Fix to add MapFunction type back

[JounQin]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and couldn’t find anything (or linked relevant results below)
• If applicable, I’ve added docs and tests

Description of changes

close #6

[ChristianMurphy]

Thanks @JounQin!
Code looks fine, it may be worth waiting for a resolution on #6 (comment) before moving forward with this.

[wooorm]

Cool that this works from an index.js. I didn’t know that.

Can you remove from unist-util-map/complex-types.d.ts in the readme as well?

For later, optional improvements:

• This line should be parent: Extract<InclusiveDescendant<Tree>, Parent> | undefined I think!
• Actual tests for the generics might be useful, such as of like this: https://github.com/syntax-tree/unist-util-filter/blob/main/index.test-d.ts

[JounQin]

For later, optional improvements

1. I'm not familiar with that part, so another PR can be raised for it.
2. The asIs mapper with import('./index.js').MapFunction<Root> alreay tests part of it, but sure a index.test-d.ts will be much better.

[wooorm]

Thanks for your hard work! Looks good to me, if other people think it’s fine to add TS 4.5+ syntax: #6 (comment)

[remcohaszing]

I think it's good to try and stick to the DefinitelyTyped support window (unless it's really inconvenient). However, I believe this only requires TypeScript 4.5 to build the types from JSDoc right? Since the types can still be consumed using the same TypeScript versions, it's non-breaking.

[wooorm]

@remcohaszing i was thinking that first, but without skipLibCheck, I was thinking maybe they'd get checked anyway?
Maybe you're right, and if that's the case then it's especially fine!

[remcohaszing]

Nope, TypeScript only looks at the .d.ts files. It's the whole reason we build them 😅

[wooorm]

Released in 3.1.2! Thanks @JounQin!