Add the `Rect::overlaps` and `Rect::contains_rect` methods

[nils-mathieu]

I stumbled on this while toying with the vello rendering engine (which is great btw, you guys are doing god's work). I'm trying to create a simple audio sequencer with it and while trying to determine whether shapes were visible on screen, I found that there was no way of checking for the intersection of two Rects.

Right now, the only way to do that is to compute their intersection, then verify whether it's empty or not.

let rect1 = Rect::new(0.0, 0.0, 10.0, 10.0);
let rect2 = Rect::new(5.0, 5.0, 15.0, 15.0);
assert!(!rect1.intersect(rect2).is_empty());

This is not ideal for two reasons:

1. It's not very ergonomic. Checking whether two rectangles overlap should probably not involve that intermediary step.
2. This is doing a bunch of wasted work to find out what the intersection is when we only care about whether it's empty or not.

This pull request adds Rect::overlaps and Rect::contains_rect, which do exactly that.

let rect1 = Rect::new(0.0, 0.0, 10.0, 10.0);
let rect2 = Rect::new(5.0, 5.0, 15.0, 15.0);
assert!(rect1.overlaps(rect2));
assert!(!rect1.contains_rect(rect2));

[nils-mathieu]

My mistake, I completely forgot about this. I just commited the suggested modifications.

[waywardmonkeys]

@nils-mathieu Could you please rebase this on top of current main to pick up the CI changes / updates? Thanks!

[nils-mathieu]

Github's autosync merged rather than rebasing without asking, I hope it's okay. Seems green though x)

[waywardmonkeys]

One last thing (from me): Could you add an entry to CHANGELOG.md? Just use the existing format, add the PR number sorted numerically and your GitHub user name sorted alphabetically and an entry for this under 'Added'.

[nils-mathieu]

done!

[waywardmonkeys]

Thanks everyone!