two finger swipe gesture implementation

[Alsan]

Add mac like two finger swipe gesture. Most of the changes are from my code formatter, hope you won't mind.

[pguedes]

hi @Alsan ,

thanks for the contribution!

have you tested this to see how it interacts with scrolling? i assumed 2 fingers were always used for scrolling... what to macs do with two finger gestures?

[Alsan]

Personally, I don't use Mac. As my understanding, there's no horizontal scroll in Mac, they use three fingers drag (the horizontal scroll bar, also apply to the vertical scroll bar) for scrolling, and two finger swipe horizontally is for switching desktop, just like I did.

My implementation, only two fingers swipe is captured. Two fingers swipe vertically or the drag event is ignored, they handled by libinput. And therefore, two fingers drag horzontally or vertically or simultaneously is possible for scrolling the window.

[Alsan]

Ok, just find someone with Mac to test the two finger horizontal scroll, they're supported with context. That means, they are scrolled when the windows with horizontal scrollbar and switching desktop if they don't.