This adds some new constructors to Rect for constructing a rect from a top-left coordinate and either a bottom-right coordinate or a width and height.

Currently, this requires constructing a rect as:
Rect(coord.x, coord.y, coord.x + size.x, coord.y + size.y)

Most of the subexpressions in that are duplicated, which creates opportunities for mistakes, such as when constructing multiple rects.

With this change, you construct as:
Rect(coord, coord + size) or Rect(coord, size.x, size.y)

This doesn't add the ability to do Rect(coord, size) since it would have the same signature. I opted to use top-left and bottom-right coordinates given the two options, since "Point" more intuitively makes sense as a coordinate than a size.