Add support to release aarch64 wheels

[odidev]

Problem

On aarch64, pip install pygit2 builds the wheels from source code and then install it. It requires user to have development environment installed on his system. also, it take some time to build the wheels than downloading and extracting the wheels from pypi.

Resolution

On aarch64, pip install pygit2 should download the wheels from pypi

@jdavid, Please let me know your interest on releasing aarch64 wheels. I can help in this.