[Feature Request] Enhancement to the Move Window to the Center keybinding

Sometimes I need to focus on the work in a single window. Moving it to the center of the screen is great for doing this. But when I am done, I would like to move it back to where it was.

It would be great if the "Move window to the center" keybinding ([#139](https://github.com/domferr/tilingshell/issues/139)) could act as a toggle and move the window back to its previous tiled position.

The above is my primary request, but it would also be handy if the size of the centered window could be specified in the configuration. Just a single set size for any window centered. If I am wanting to center a window, I might be wanting to make it bigger to focus on it more.

Thank you.