Move prop-types library to devDependencies

[eugef]

As react and react-dom are already defined as devDependencies i propose to to the same with prop-types.

Are there any cons?

[nkbt]

prop-types are used in prod build, but react-dom is not. So they have to be in deps.
Alternatively in peer deps

[eugef]

react is also used in prod build but it is not in dependencies list. This makes sense and allows to avoid transitive dependencies and ending up with multiple instances of react in one project.

The same approach should work for prop-types - moving it to devDependencies and peerDependencies

[nkbt]

yeah, peer deps would do just fine

[eugef]

@nkbt please review my PR #56