ncm2-tmux

Provide word completions from other tmux panes for ncm2.

The idea was stolen from wellle/tmux-complete.vim, since I misunderstood its source code and believed that it tends to block vim at the time I created tmux completion for the old nvim-completion-manager.

You could use wellle/tmux-complete.vim directly since it supports ncm2 and doesn't block vim actually.