Add SearchProvider2 and ResultMeta interfaces to types module

[LumenGNU]

I made the changes requested in the comment to PR #89 - moved the SearchProvider2 and ResultMeta interfaces to the types module.

However, I encountered a problem: I couldn't import these interfaces in my test project. (nor any other types from the types module).

Is there any documentation or recommendations on how to properly import types from the types module?

Perhaps I misunderstood the comment, and these interfaces should still be re-exported through extensions/global.d.ts?

[swsnr]

@LumenGNU Please update your existing pull request #89 instead of opening a new one, otherwise it's hard to keep track of review conversations.

I'm closing this one.