H5游戏这里有一个坑。背景音乐的问题。
creator H5声音背景播放问题
The AudioContext was not allowed to start. It must be resumed (or created) after a user gesture on the page. https://goo.gl/7K7WLu
因为需要玩家主动点击后才能播放，所以，需要监督玩家点击了后，才播放背景音乐。
AudioManager.resumeBGM(); 还原一下播放也可以。
https://developers.google.com/web/updates/2017/09/autoplay-policy-changes#webaudio 的指南：
Key Point: If an AudioContext is created prior to the document receiving a user gesture, it will be created in the "suspended" state, and you will need to call resume() after a user gesture is received.
