Glider mechanic

This update adds a glider to the game. You get it near to the end of the game and you can use it by holding the jump button (C or J).

I wanted to add some variety to the gameplay so that I can stretch the length of the game a bit. I felt like the existing mechanics (very basic platforming + grappling hook) just weren't enough for a complete game. I'm hoping this suffices and to find it out, I'll be focusing on level design for the next few iterations.

Cheers!