Improve types for ArcdePhysics.closest

[ef4]

This uses generics so that the return type from closest() is narrowed to match whatever type you passed in for the targets.

I also clarified that the return type always includes null (which is what the implementation returns when it gets an empty list of targets).

And I clarified that the source needs to be Vector2Like.

Resulting typescript diff:

--- a/types/phaser.d.ts
+++ b/types/phaser.d.ts
@@ -70565,7 +70565,7 @@ declare namespace Phaser {
                  * @param source Any object with public `x` and `y` properties, such as a Game Object or Geometry object.
                  * @param targets The targets.
                  */
-                closest(source: any, targets?: Phaser.Physics.Arcade.Body[] | Phaser.Physics.Arcade.StaticBody[] | Phaser.GameObjects.GameObject[]): Phaser.Physics.Arcade.Body | Phaser.Physics.Arcade.StaticBody | Phaser.GameObjects.GameObject;
+                closest<Target extends Phaser.Physics.Arcade.Body|Phaser.Physics.Arcade.StaticBody|Phaser.GameObjects.GameObject>(source: Phaser.Types.Math.Vector2Like, targets?: Target[]): Target | null;

                 /**
                  * Finds the Body or Game Object farthest from a source point or object.
(END)