Updated unlock method docs

Author: pavle-goloskokovic

v3/src/sound/webaudio/WebAudioSoundManager.js

@@ -81,7 +81,11 @@ var WebAudioSoundManager = new Class({
         return sound;
     },
     /**
+     * Unlocks Web Audio API on iOS devices on the initial touch event.
+     * Read more about how this issue is handled here in [this article](TODO add link).
+     *
      * @private
+     * @method Phaser.Sound.WebAudioSoundManager#unlock
      */
     unlock: function () {
         var _this = this;