feat: export types from main entry point

[lumirlumir]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

In this PR, I've exported all types from src/types.ts through the main entry point.

Previously, to access the global types defined in src/types.ts, they had to be imported from @eslint/markdown/types. After this change, they can be imported directly from @eslint/markdown.

What changes did you make? (Give an overview)

To enable importing types from the main entry point, I used a small trick.

The types.ts file is built into types.js and types.d.ts.

In the built types.js, it's possible to re-export the type declarations from the main entry point using export * from "types.js".

However, that wasn't possible in the source. To bridge the gap, I added a dummy src/types.js file so types can be imported from src/types.ts.

Related Issues

Ref: eslint/json#130, eslint/json#130 (comment), #453, #367 (comment)

Is there anything you'd like reviewers to focus on?

N/A

[fasttime]

LGTM, thanks. Leaving open for a second review.

[JoshuaKGoldberg]

Great! IMO a single almost-blank file is not a very high price to pay for easier type imports.

Thanks for pushing on this @lumirlumir!

[lumirlumir]

@JoshuaKGoldberg Thanks for understanding that I took on the issue you originally suggested.

[nzakas]

LGTM. Thanks.