Allow snapping a window to screen corners about labwc

[Nosirus]

I would really like that too, on wayfire I can use the corners to hang the windows with the mouse.

If we can define directly like with the regions that would be great

[Bezzumnbiu]

Good idea, I wrote about adding this thing earlier

[johanmalm]

I like the sound of this.
Best to merge this after 0.7.2

[tsujan]

I used it a lot with kwin_x11. When I saw that it was missing in labwc, I defined right click actions on title-bar buttons for snapping to corners, but a direct mouse snapping will be much more comfortable.