Update readme to point to other_video_transcoding

[pefoley2]

Hi, I ran into some issues with transcode-video failing to scan a mp4 file that mp4track didn't understand.
I only realized that the newer other_video_transcoding repo existed because it was mentioned in one of the issues.

Would it make sense to add a note to the README like https://github.com/donmelton/video-transcoding-scripts has?

[lisamelton]

@pefoley2 That's a good question! I will consider something like that. Thanks!