Fully type module then mark as `py.typed`

[Avasam]

This is an issue to track jaraco.clipboard being marked as py.typed. I'd rather not lie about the typed state of a library and wait until all its public members are fully annotated (or at least to a "best effort") before being marked as py.typed.

Refs:

• https://github.com/jaraco/skeleton/issues/98
• https://github.com/jaraco/skeleton/pull/136#discussion_r1714057809
• https://github.com/jaraco/skeleton/issues/143