New update for Nexus!

Added an update that includes:
-Background music(doesnt work for browser play i dont know why)

-New Menu

-Dash when right clicking, Invincibility when dashing

-+3 hp for player and +5 hp for Nexus when reaching lvl 7

- Up to lvl 20 (before it was only 8)

-Major Bug fixed(before, when reaching lvl5 and up there is a possibility that enemies wont spawn)

Large thanks to my friend, Keej, for suggesting me this updates.