The code isn't all that pretty, but it's easy to modify and tune to test what
works well.
I've opted to keep the workspace menu's smooth scroll implementation. When
swiping it's necessary to wait for a button press on the desired space since the
pointer can be anywhere. As such making sure that the workspace stack always
ends up in a discrete state isn't that useful, so I opted for more control when
swiping.
We should add some preferences that users can use to tune the speed of swiping.
I assume that this can vary quite a lot between different touchpads.
