expand/shrink rectangle functions

[dennisorlando]

• added shrink function to rectangle (mutable)
• added "shrunk" function to rectangle (copy)
• added expand function to rectangle (mutable)
• added "expanded" function to rectangle (copy)

[QuantumBadger]

Thank you for this, and sorry for the big delay in reviewing.

Would it be possible to make the following changes please?

• Remove the mutable versions, and rename the copy versions to shrink and expand (for simplicity)
• Add some tests to ensure this is working correctly -- I think in some places this may be adding instead of subtracting, and vice versa.

[dennisorlando]

Thank you for this, and sorry for the big delay in reviewing.

Would it be possible to make the following changes please?

* Remove the mutable versions, and rename the copy versions to `shrink` and `expand` (for simplicity)

* Add some tests to ensure this is working correctly -- I think in some places this may be adding instead of subtracting, and vice versa.

How would we handle when we want to shrink a Rectangle that is contained in another struct? If we only make copies then wouldn't it mean that we either have to replace the Rectangle with a new one (not sure how ownership handles that, I might be messing up) or manually modify the fields of the rectangle?

[dennisorlando]

I'll write some tests as I find some time, I'll have to remember to do that tho 😆 😮‍💨
I've currently only tested it locally (on a project that I'm working on) where it appears to be working