Allow customization of tiling steps per direction/corner

[JonnyCodewalker]

Possible partial functionality overlap with !23

Currently the extension allows customizing tiling steps for center and side tiling.
I think expanding this to allow a more fine grained control would be useful.

As an example (what I would like to use) :

• center tiling: 1 , 0.5
• left/right side tiling: 0.5, 0.65 , 0.35
• top/bottom tiling: 0.5, 0.65 , 0.35
• corner tiling : 0.5, 0.35

The reason for me is that corner .65 has no real use. If I need a large window I either go .65 top/bottom or sides.
The fact that this however can not be configured results in me sometimes having to corner-tile multiple times to get the desired result.

If I have time on the weekend I might dig into the code to see if I can provide a PR. However I am not familiar with js and gnome-extension programming, so no promises :)