cancelCompression returns null on Android

[guy-plentific]

The cancelCompression method causes the Future<MediaInfo?> compressVideo() method to resolve to null. On iOS it is resolved as expected to a MediaInfo object with isCancel set to true. The cancelCompression method does seem to cancel the compression operation on both platforms.

I notice there is still a TODO, "Add cancel function to Android" in the package readme, however the change log entry for v2.1.0 states Added cancel compression to android, therefore I'm guessing the TODO was incorrectly left in the readme? This has been tested on both physical Android and iOS devices

To provide consistency between platforms, and match expected behaviour, we would expect the cancelCompression method to cause a running compressVideo to resolve to a MediaInfo object.