Incremental :normal

Experiment with preview of :normal commands. Also probably the most insane multi-cursor implementation for nvim.

To activate, use :[RANGE]norma to place a cursor at the beginning of every line in [RANGE]. (As a safe guard, it only activates on this spelling, not :normal nor :norm) Then type normal-code commands completely as normal.

Demonstrates:

• Abusing <Expr> and timers to execute commands in command-line mode.
• Abusing g:Nvim_color_cmdline and timers to trigger code on cmdline change
• Using redraw! to display a temporary buffer state
• Some crashes and weird behavior that needs investigation