Expose a CursorPosition resource #5034
Description
What problem does this solve or what need does it fill?
Knowing where your mouse is is useful and should be ergonomic.
What solution would you like?
Store and update a CursorPosition resource, which reads from the Window resource to store an Option<Vec2> representing the physical position of the mouse (or other cursor).
What alternative(s) have you considered?
Compute this manually every time it's needed.
Additional context
This will be impacted by #4530, which will move where this data is stored.
Better APIs to convert between world space and screen space coordinates will make this functionality even more useful; we should add methods on MousePosition to do this once those are established.