Introduce a "Pets" feature to Theta Wave

[tigleym]

Pets aid the player in battle by also firing projectiles at enemies, or even using unique skills/abilities that could be helpful in combat.

[cdsupina]

A key behavior for a pet/follower would be that it follows the player. A good place to start would be adding this as a movement function for Motion2DComponent. The function could be called follow_target.