[Feature] mypy typings

[bryanforbes]

Currently, asyncpg is untyped and has to be ignored as an import when using mypy. Because of this, I created an asyncpg-stubs package generated from stubgen that I use in my own projects as a git dependency, but it would be great to have these in the main library (and verified by the developers). If this is something that is desired, I would be willing to create the initial PR.

[1st1]

Yeah, we would love to see typing support in asyncpg.

[cstigen]

Any update on whether asyncpg-stubs is planned to get merged into asyncpg?