Remove useless files in Zig package

[Corendos]

Closes #87

I wasn't sure if "include/" could be required. The only usecase I see is if someone uses the Zig build system for a C project and wants to use libxev as a C library.

[paperdev-code]

The only usecase I see is if someone uses the Zig build system for a C project and wants to use libxev as a C library.

Sounds like a valid use case to me. It's only one file so I think it hardly hurts.