feat: zig support

[LDprg]

This is related to #929. I tried adding my own zig support, not sure if I did everything right.

I just want to note that zig does only support line comments (// or /// or //!).

[jdkato]

I'd like to add support for new code languages through tree-sitter, rather than the now-deprecated method of regex.

Vale uses github.com/smacker/go-tree-sitter, which doesn't include Zig by default.

You can either contribute to that repo or create your own Go package for Zig.

I did something similar for Julia: package, source.