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I find myself wanting this API quite a lot, and I imagine it'll probably
be useful for others.
# What?
This PR adds `Rect::scale` and `Rect::scale2` functions, which work a
lot like `expand`, but instead multiply by a scale.
i.e.
```rs
rect.scale(2.0); // rect is 2x as big, still in same center
rect.scale2(vec2(1.5, 2.0)); // rect is 1.5x as big on x axis, 2.0x as big on y axis. still in same center
```
# Why?
Before this you either had to write this yourself or use a `expand` in a
cumbersome way:
```rs
rect.expand2(vec2(rect.width() * scale.x / 2.0, rect.height() * scale.y / 2.0));
```
I find myself wanting to scale things up by a factor frequently enough,
and it seems like a useful addition to have a multiply-based variant of
`expand`.
I realise this is pretty minor, but it seems useful enough to me!
---------
Co-authored-by: zkldi <20380519+zkldi@users.noreply.github.com>
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
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