Add missing chart difficulties generation tool

[geovannimp]

Me and my friends are new to Clone Hero, at least playing on a guitar, and is a really bad experience to find a chart for a music that you want to play and is basically impossible for our skills.

After some search I found this tools that can convert charts to other difficulties from expert.

I converted the tool to typescript and added it as a tool in the toolsbar and in the settings as experimental.

Know problems:

• SNG is not supported yet, I don't know how to pack it again after generating the difficulties, but should not be hard

Future implementations:

• Add preview function to generated difficulties
• Once Add Library #88 is done, we can add a button to generate on charts with missing difficulties