Add support for multiple tabs in panes

[9gcity]

It would be great to be able to have different tabs in a single pane, so you can switch out tabs in panes without needing to switch the overarching tabs, and I don't think this functionality is currently provided by zellij either.

[har7an]

Hi, thanks for reporting this!

I'm finding it hard to imagine how this feature would integrate into the application, so I have a general question on user interaction: How would you wish to control a panes tabs over the general application tabs? I.e. when using the application, how would you switch only tabs inside a given pane?

[9gcity]

Maybe using differents buttons for window tabs and pane tabs? So switching between window tabs could be Ctrl+T (for example), while pane tabs can be Ctrl+Y or something?