feat: add a window drag resize task

[tsuza]

When implementing a custom title bar, most things are straight forward: minimizing, maximizing, closing, dragging, and the context menu. However, there is one small issue: resizing. Since you have to turn off decorations, the border also gets disabled, and there is no easy way to specifically enable that through winit ( afaik ).

This PR exposes winit's drag_resize_window to give an easier time to resize the window, which is especially useful for the case I mentioned above.

Hopefully everything is up to standard!