implement TmuxSend command
implement TmuxSend command

modify function `s:TmuxSend` to take optional argument
- for ease of use
  - wrt `TmuxSend` command

wishlist item: tpope/vim-tbone allows character-wise visual selection
- |     " if in character-wise visual or select mode
  |     if mode() =~# '[vs]'
  |       " get line/column of visual selection marks
  |     endif

credit
- tpope/vim-tbone/plugin/tbone.vim
- https://vi.stackexchange.com/a/11028

atweiden/pacfiles,atweiden/pacfiles