Copy configs from typeshed project
Add stubtest to github action

This commit fixes the issue pointed out in:
hahow/pika-stubs#9

Namely `int` and `float` not (statically) evaluating as subclasses of
their abstract types in `numbers`:
python/mypy#3186

These abstract types have been replaced with their concrete equivalent.
Note that this does not match the code in pika, which *does* compare
against e.g. `numbers.Integral` at runtime. But the documented API only
mentions concret types (i.e. `int` and `float`) so this is considered a
reasonable compromise.

addresses hahow/pika-stubs/issues/9