tmux percentage pane sizing

[deliciouslytyped]

I was peeking through the tmux 3.0 changelogs and this entry caught my eye:

* Add support for percentage sizes for resize-pane ("-x 10%"). Also change
  split-window and join-pane -l to accept similar percentages and no longer
  document -p.

If that is what I think it is, it would be interesting to have support for such relative sizes in tmuxp.

[denisw]

It seems as if percentage sizes work just fine with the existing tmuxp size options. I just tried the following successfully:

session_name: percentage-pane-size
windows:
  - window_name: example
    layout: main-vertical
    options:
      main-pane-width: '60%'
    panes:
      -
      -

That being said, it would be great if such a percentage were used by default for main-pane-width / main-pane-height, to avoid the situation on large screens were the "main" pane is actually much smaller than the other ones (see #314).