[Request] Sort by Difficulty

[MasterTim17]

Hello,
it would be great if songs can be sorted by diffuculty. So when i have a visitor, he/she can select normal/hard songs :)

[brianhuang822]

Added a PR last Friday, hopefully repo owner gets it merged and released 👍

[halsafar]

Instead of sorting solving this with filters seems better. Guarantees any sort method will have the difficulty you want.

@brianhuang822 work did get merged for the next release, despite the pull-request having issues, it was manually merged.