Adjustable touchpad scroll speed

[Icelk]

Thanks for working on egui, it is very impressive!

Is your feature request related to a problem? Please describe.

Scrolling with my trackpad on Wayland is very slow and I see no way to change it.

Describe the solution you'd like

An option in Context::options to set a factor which smooth_scoll_delta is multiplied by in scroll_area.rs.

Describe alternatives you've considered

line_scroll_speed doesn't affect touchpads, only mouse wheels.

Additional context

[Icelk]

Seems like acceleration doesn't work either. Probably some winit issue...