docs(fix): install hast types in development only

[felixranesberger]

Hi, I just read your documentation and think that installing the @types for hast should probably only be done for development only.

[ChristianMurphy]

It depends on the use case.
As a library dependency is the only correct way, it needs to go downstream.
As an application it could go either way.

[remcohaszing]

There are use cases where types (or anything really) may be a dev dependency. Whatever it is, depends on the project. For most use cases this is false. IMO we leave the instructions as-is.

[wooorm]

It depends! There are also cases where other flags are useful. This section isn’t always 100% right for everyone and that’s fine. For me, it signals that it’s on the npm registry, and what the exact (scoped) package name is!

Thanks for thinking of this!