Start button for creep rounds

this is for the features "User should be able to press start for creeps
to spawn" and "User should be able to lose lives when a creep reaches
the end point"

steps to add component in
import file

attach MainGUI (script) to Main Camera

attach CreepSpawner (script) to an object

- set size of Prefab, Amount In Round, and Spawn Delay to the amount of
rounds intended

- under Prefabs, set the Elements to the creep objects in Prefabs folder

- set the Amount In Round Elements to the amount intended to be in each
round

- set Spawn Delay Elements to the amount of time intended to be between
each creep in a round

- set Hip Points to the HP text object
attach the HPBehaviourScript to the HP text object

- set Hp to intended hit points of player