fix(ios): currentPosition and duration may never equal during playing

[Phecda]

Problem

When play a remote file on iOS, currentPosition may never get to duration, which makes it difficult to know whether the playing is end.

Solution

Add an observer to native player end event, and in that observer, force trigger another playback event, where currentPosition is set to be duration. Note that at this moment, playerItem.currentTime is still smaller than duration, so we cannot use that value.

may fix #328

[shahid-vorksol]

same issue on android...

[hyochan]

This looks promising! Let's ship it 🚀