Create goalkeeper movement function

[afpola]

Ideas for game/game changes:

Ball is still, reacts to contact w player.

• Might be a good idea to make the entire upper edge the goal, then make the goalkeeper like a wide line/big object so it's still challenging to score.

Alternatively ball is set at point x,y or z etc and then moves in some downwards direction.

Goalkeeper is moving sideways in a set pace.