Updating how wheels are being built. Fixing py36,37 support

[martinhoyer]

As mentioned in #5, current netifaces2 wheels are broken on python3.6. PyO3 dropped 3.6 support in 0.16.
I've tried to update the build process to increase compatibility and switch to building py37 abi3 wheels.

• Linting step was failing on install: Fixed by installing maturin
• Moving to manylinux_2_28
• Cross compiling linux wheels to more architectures
• Building musllinux wheels
• Touching up the pyproject.toml
• Trying (ugly) py36 wheel building. Needs changes in Cargo.toml and pyproject.toml before being build.
• In defs.py, there is from typing import Literal, which was only introduced in 3.8:
  Solved by using [typing-extensions](https://pypi.org/project/typing-extensions/).

So far I only tested the linux py37-abi3 x86_64 wheel on Python 3.9 (el.8) and cpy36m manylinux2014 x86_64 wheel on Python 3.6 (el.7), both seemed to be working fine.

[SamuelYvon]

All passed, looks good to me. Will merge; for the sed hack if you think of something else feel free to lmk, I'll try to come up with a better solution but I'm not sure there's an obvious one.