Allow changing continuous scrolling frequency

[FireChickenProductivity]

Some users will want to be able to scroll slower than currently possible with a scrolling speed of 1. The only way to allow that would be to allow changing the continuous scrolling frequency, the frequency with which the code calls the scrolling action.

[nriley]

In the community backlog session we discussed that this could be implemented by setting a minimum scrolling speed. If the scrolling speed is < 1, it would affect the scrolling frequency (e.g. 0.5 = scroll half as often).