Enhancement: Scroll speed multiplier + Slider Velocity modcharting

[daisukidaisy]

Scroll speed multiplier: Instead of a constant number like what Kade Engine has, a scroll speed multiplier would take the value from each chart and multiply it by a given value. This would probably be more compatible with the idea below.
Slider Velocity (SV): A common form of modcharting that alters the scroll speed of the song mid-chart. There are good examples of this type of modchart dating back to early 2000s DDR at its roots. This is related to the other idea so I thought I'd put both in one issue.

[Leather128]

I mean right now you can already technically change the scroll speed mid song with modcharts, but I do think I'll add the scroll speed multiplier thingy, just because it seems like a good idea.

[flowerbearttv]

I mean right now you can already technically change the scroll speed mid song with modcharts, but I do think I'll add the scroll speed multiplier thingy, just because it seems like a good idea.

I tried putting setScrollSpeed(5) in a modchart to test it and it didn't work so

[NeverStopWinning]

100th yay