Beta_v1.5 release notes

Hello, and thanks for checking out the first release version of Asteroid Swoop (Beta_v1.5)!  Since this is the first public release, please let me know if you encounter any bugs I've missed during testing.

• Major feature notes
  • 20 increasingly difficult waves to survive, plus one randomized Bonus Wave.
  • 6 unique enemies to deal with.
  • 4 different building types to construct and upgrade.

• Beta v1.5 additions
  • Added the Bonus Wave after wave 20.  The bonus wave lasts up to 99 seconds and spawns entirely random objects alongside frequent UFOs, survive as long as you can and gain extra score to boost your final total.
  • Added Hard Mode.  Hard Mode can be toggled by holding tap/click over the wave number icon before starting the first wave.  In hard mode your colony has fewer buildings that are further apart, and a bonus x1.25 is added to your score at the end.