Support for HEVC video

[ChristopherLinnett]

The plugin doesn't seem to be able to read HEVC video. I have noticed it when trying to generate thumbnails that use this format (GoPro video mostly).
I won't have control over the types of videos the intended app users will try to use so being able to read these formats is essential.
The message that shows when attempting to process these videos for a thumbnail is this:

couldn't generate thumbnail, error:Error Domain=AVFoundationErrorDomain Code=-11832 "Cannot Open" UserInfo={NSLocalizedFailureReason=This media cannot be used., NSLocalizedDescription=Cannot Open, NSUnderlyingError=0x283585c80 {Error Domain=NSOSStatusErrorDomain Code=-12431 "(null)"}}