Support deleting the Zig cache

[orhun]

Hey, thanks for this tool! 🐻

I realized kondo doesn't delete the Zig cache folder which is usually zig-cache.

If appropriate, I would like to submit a PR for this!

[tbillington]

Hey! Absolutely, it should be relatively straight forward, here's an example adding swift

https://github.com/tbillington/kondo/pull/76/files