Fix HLS on Android 9.0

[hunterjm]

This fixes #2948. The issue is Chrome on Android 9.0 was returning "maybe" for canPlayType (docs), but was unable to actually play the media. This PR checks HLS.js before "native" support, then falls back to MJPEG.

[hunterjm]

Hold off on this. Apparently iOS Safari returns maybe here. Will need to check HLS.js first, and fall back to native before going to MJPEG.

[hunterjm]

The latest commit is confirmed working in Chrome and Safari on their respective mobile emulators (Android 9.0, and iOS 12) and desktop.

[balloob]

This is weird. Does hls better check for supported than native? We can check the return type of can play too

[hunterjm]

So HLS.js just have to check if MediaSourceExtension is supported, which is an easy check on the window. I have no clue why canPlayType returns an empty string, maybe, or probably. All 3 of them sound pretty uncertain. All the demos I’ve looked at use HLS.js first and fallback to canPlayType, then unsupported.

[balloob]

https://developer.mozilla.org/en-US/docs/Web/API/HTMLMediaElement/canPlayType