Provide good error message when the type is capitalized

[chenglou]

Hot newcomer path probably.

[IwanKaramazow]

type something = {
  types: array<SuperType>
}

[evelant]

@chenglou yeah, it tripped me up almost immediately starting out with rescript. The Did you forget a `.` here? message is quite misleading. It seems that message shows up in a bunch of cases where it isn't very helpful to newcomers.

[stale[bot]]

The rescript-lang/syntax repo is obsolete and will be archived soon. If this issue is still relevant, please reopen in the compiler repo (https://github.com/rescript-lang/rescript-compiler) or comment here to ask for it to be moved. Thank you for your contributions.