Support precompiling NIfs

[maennchen]

It would be awesome if it was possible to precompile (and possibly cross-compile for different architectures) the Nifs for published libraries. This would make the installation by the user of the library a lot and removes the requirement to install Zig.

This has already been done by other Nif providers like rustler:
https://github.com/philss/rustler_precompiled

It usually works by building the nifs and adding the object files to a GitHub release.

When a user installs the library from Hex, the library looks if the files exist locally and downloads them from the release if not.

[ityonemo]

yep. This is on the todo list in VERSIONS.md I will try to do it for 0.14 (thought I had an issue up for it but i don't see it anymore)