Feature: Move panes directionally

[kunalmohan]

Fix: #164

[kunalmohan]

I've added a separate Move mode which can be toggled on/off with Ctrl+f. When in Move mode, one can see the arrow keys to move the current pane directionally.

[imsnif]

Hey, this looks great!

I only have two comments:

1. I know finding free keybindings is hard, but ctrl-f is command-completion in fish. Can we find another one?
2. When we resize panes, we need to also send a message to the terminal's pty that it has been resized so that the application inside the pane knows about its new size. We do it like this:

   zellij/zellij-server/src/tab.rs

   Lines 789 to 793 in b94b25c

   	self.os_api.set_terminal_size_using_fd(
   	*pid,
   	pane.get_content_columns() as u16,
   	pane.get_content_rows() as u16,
   	);

[kunalmohan]

I know finding free keybindings is hard, but ctrl-f is command-completion in fish. Can we find another one?

How about Ctrl+h or Ctrl+x or Ctrl+v or Ctrl+b or Ctrl+n?

[imsnif]

I think ctrl+h is good. It's an alias for backspace in bash, but I guess one can use backspace as a workaround (or remap it)

[kunalmohan]

@imsnif This keybind_test here is failing. I'm not familiar with this part of the codebase, so any ideas about how I would go about fixing this?

[imsnif]

I'm not familiar with those either I'm afraid :/ If it were me I'd try to debug and compare to main, see what they expect and what's going wrong.

Also btw - be sure to test that with the ctrl-h shortcut we can still use backspace - might be awkward otherwise :)