Add static Lerp method on Vector2

[GregDevProjects]

Please do not update the README or Change Log, we will do this when we merge your PR.

This PR (delete as applicable)

• Adds a new feature

Describe the changes below:

Adds a static method to the Vector2 class so that two vectors can be lerped (if that's a word 😛 ) without modifying the original Vectors.

Resolves #5684.

[samme]

Since Vector2 has no static methods maybe the new method could go on Phaser.Math instead, like Phaser.Math.RandomXY()?

[GregDevProjects]

@samme sounds good, there's a Linear static method on the Math class that does the same thing with a Number, so I named this function LinearXY - the XY is intended to specify that a Vector2 will be returned.

Any chance you'd be willing to add the hacktoberfest-accepted label to this PR? 😅

[photonstorm]

👍