I've set `lexical-binding` to `nil` in all Emacs Lisp files to suppress
the warnings introduced in Emacs 31 requiring all elisp files to have a
`lexical-binding` comment.
This retains the default behavior of dynamic binding when no
`lexical-binding` comment is present. With it set to `t` across the
board, various things break, and fixing those is a task for another day.
It has issues with linum-mode, so currently linum-mode needs to be
manually disabled. I will make it automatically toggle linum-mode when
enabling/disabling writeroom-room at some point.