Add missing dependency

[Ayc0]

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

Add @types/unist in dependencies (in the deps and not devDeps, because those types are exposed to users)

Related to #12

[Ayc0]

@wooorm, I didn't know which version to choose, so I just picked the latest

[Ayc0]

I could also use peer deps instead of deps, WDYT?

[ChristianMurphy]

Thanks @Ayc0!
The rule of thumb for picking versions in unified.
Generally go for the first release of the latest major and use ^ to allow for newer releases in the same line.

[Ayc0]

Thanks @ChristianMurphy

And what about deps vs peerDeps?
Any preferences?

[ChristianMurphy]

I'd lean depedencies.
peerDependencies should be used sparingly, and specifically where either: a user needs to be able to select another version of a package, or the location of a package's folder relative to another package is important.
Here the relative folder isn't important, and selecting a specific version of the dependency manually is unlikely and could cause issues.

[Ayc0]

Thanks!

[wooorm]

Thank you Benjamin!