设置 AudioSource 的优先级。
Unity virtualizes AudioSources when there are more AudioSources playing than available hardware channels.
The AudioSources with lowest priority (and audibility) are virtualized first.
Priority is an integer between 0 and 255. Where, 0 = high priority, 255 = low priority.
WebGL: This setting doesn't affect WebGL because there is no limit on the number of audio channels in the WebGL platform.