neovim's pkg-readme points at libtermkey's readme, but nvim no longer
depends on libtermkey.

Is the esc thing still an issue? It seemed ok for me in a quick test
without touching tmux config, but I'm not using nvim full time so might
not notice. If it is, the relevant part from libtermkey readme should
probably be copied to nvim's, if not, drop the section?