Computes the intersection of the two given rectangles.
The intersection in the image above is the blue outline.
If the two rectangles do not intersect, res will contain a degenerate rectangle with origin in (0, 0) and a size of 0.
| this |
a Rect |
| b |
a Rect |
| res |
return location for a Rect |
|
`true` if the two rectangles intersect |