Allow centering panel horizontally

[vlucki]

When editing code for longer periods of time, it can put a strain on users having to constantly look to the left. This problem becomes worse on ultra wide monitors.

To get around this, one must either move the code of interest to a right split, so that the left-aligned text at least starts at the center of the monitor, or split the editor in 3, manually moving code to the center panel. Neither is an ideal workflow.

Noevim has a plugin called "no-neck-pain" to ensure things are always centered regardless of the width of the editor. The Focus editor allows setting a max editor width which achieves similar results. VS Code also seems to support something along these lines.