Allow for mouse wheel scrolling to be converted to up/down arrows for tmux/screen/vim copy mode

It would be really nice to have a way to use external mouse scroll wheel or trackpad scrolling to simulate up/down (maybe even left/right) arrow key presses. Maybe a toggle in the settings window to switch between normal window scrolling behavior and simulated key presses.

Thanks!

No files, tests, or entry points are named in the issue. Start by locating the iOS mouse or trackpad input handling and settings code; done means scrolling can optionally produce arrow-key events for tmux, screen, or Vim copy mode while normal scrolling remains available.

Written by the indexing model from the issue text.