feat: allow specifying imports to be ignored during the DTS file generation

[minenwerfer]

Description

This PR adds the feature to specify imports to be ignored during DTS file generation via the ignoreDts option. This feature solves a problem I'm having in production (#408) by enabling some imports to be auto-imported while preventing them to be put in the generated DTS file. This way I can declare them myself as needed without running on conflincts.

It also solves a little bug I found. Despite ignore (and now ignoreDts) being declared as (string|RegExp)[]|undefined in the Options they were being compared using a strict equal only, so regexes would always fail. I solved this by creating a small helper function. If it was the expected behavior in the first place please let me know.

The API is as following:

const options: Options = {
  // ...
  ignoreDts: [
    'ignoreThis'
  ]
}

[minenwerfer]

Hey @antfu , can you have a look at this PR?