Chords in Real Songs: support iOS

See some progress here: [https://github.com/ShacharHarshuv/open-ear/pull/275](https://github.com/ShacharHarshuv/open-ear/pull/275)

Seems like it's not going to be possible natively, but it might be possible to do a workaround to make it available in the web version, as long as the user manually plays the video