add builtin regex function

[billy-yoyo]

Context

This adds the Rust Regex package as a dependency and adds a simple regex function (without a glyph alias) which executes a pattern and returns a list of boxed strings representing each of the matching groups.

I also added a hashmap cache to the Uiua environment, which we use as a pattern cache.

Let me know if you'd like any changes.

[billy-yoyo]

actually just realized this might not handle error situations very well, will add some more tests later

[kaikalii]

Great work!
I'd like to request one change.
Rather than having the cache as part of the Uiua struct, can you make it a thread-local?.
That way calling regex won't have to lock anything.

[billy-yoyo]

Will do, probs won't have time tonight but maybe tomorrow

[billy-yoyo]

@kaikalii changed the cache to use a thread local and also added some recovery code (invalid pattern, 0 matches) so it should be more stable now.

[billy-yoyo]

looks like build is failing for using an unstable feature, will look into implementing around it tomorrow

[billy-yoyo]

That's slightly annoying, the feature it's erroring for because it's unstable has been all but approved: rust-lang/rust#92122

Not sure if there's a way to disable this error as it's not really important based on that rust Lang pr

E: can just add the feature flag to the crate flag, will do it tomorrow

[kaikalii]

Why not just use .with(...)?

[billy-yoyo]

@kaikalii changed with_borrow_mut to with followed by a borrow_mut