Proposal: rename or alias Vector.size to Vector.magnitude

[mattjennings]

Context

This is something that I repeatedly get tripped up on. It seems best to match Vector properties/methods to their mathematical operation. In Excalibur that's mostly true except magnitude is size, and I always forget. Most vector libraries also seem to name their magnitude property/method as magnitude

Proposal

Deprecate size in favour of magnitude

[eonarheim]

@mattjennings totally agree