Experiment in making the editing experience not suck when maximized on an ultrawide montior.
Currently, just makes a scratch window to the left of the main window. The
WinResize event is watched in order to declaratively auto-resize/close/create
said scratch window, keeping the main window in a place where if it were 80
characters wide it would be centered.
This is also maybe a long-term project in declarative Neovim window management, hence the name "winpolicy".