Use manylinux2014 to supply aarch64 wheels

[uSpike]

Hi, thank you for this project!

It'd be useful for those like me running on ARM systems like the Raspberry Pi, to install pynng from a wheel and not rely on the system nng. https://www.python.org/dev/peps/pep-0599/ specifies aarch64 and it is being rolled out on many other projects such as numpy

Cheers!

[codypiersall]

Thanks for opening the issue!

Coincidentally, I'm working on aarch64 at the moment as well, and yeah, building from source is a bit of a pain for me too. I won't be able to work on this soon, but I'll leave this issue open to track that this would be a good thing.