Allow web audio unlock via mouse click

Scenario in Chrome for desktop:

1. Game loads
2. Game automatically starts some playing music (web audio, not HTML5 audio)

- If the user pressed a key or clicked the canvas with the mouse before the music started playing, they now hear the music.
- If the user did not press a key, nor click the canvas with the mouse before the music started playing, they will not hear the music until they press a key, however no amount of mouse clicking will let them hear the music.

This fix allows a mouse click to get the music playing audibly, even if they didn't interact with the canvas (via keyboard or mouse) before it started playing.

Author: Joncom

lib/impact/sound.js

@@ -35,11 +35,13 @@ ig.SoundManager = ig.Class.extend({
 			this.audioContext = new AudioContext();
 			this.boundWebAudioUnlock = this.unlockWebAudio.bind(this);
 			ig.system.canvas.addEventListener('touchstart', this.boundWebAudioUnlock, false);
+			ig.system.canvas.addEventListener('mousedown', this.boundWebAudioUnlock, false);
 		}
 	},
 
 	unlockWebAudio: function() {
 		ig.system.canvas.removeEventListener('touchstart', this.boundWebAudioUnlock, false);
+		ig.system.canvas.removeEventListener('mousedown', this.boundWebAudioUnlock, false);
 
 		// create empty buffer
 		var buffer = this.audioContext.createBuffer(1, 1, 22050);