could you please add a setCaptionListener in ExoVideoView.java

[zengxin]

• I have verified there are no duplicate active or recent bugs, questions, or requests

Include the following:

• ExoMedia version: 3.0.0
• Device OS version: 6.0
• Devide Manufacturer: Huawei
• Device Name: Nexus 6P

Reproduction Steps

Expected Result

Could you please add the following function in ExoVideoView.java?
So that I can use it to support Closed Caption
Thanks

public void setCaptionListener(CaptionListener captionListener) {
    this.captionListener = captionListener;
    emExoPlayer.setCaptionListener(captionListener);
}

Actual Result

[brianwernick]

Duplicate of #115