Changelog:
- Move sprite to emitter itself to allow better reusing emitter config
- Dedicate a function for destroying entity. This is helpful for dealing
with events that only occurs during entity destruction
Changelog:
- Config should contain constants that determine the spawning of an
emitter.
- Move user_data and update_func to emitter, since these values can
change depending on the scene.
- Assets now load in Emitter Configs