Spawning tmuxp sessions from within tmux 2

[gerazov]

Awesome project guys :sunglasses:

Following Primeagen's bindings I made a binding for opening tmuxp sessions from within tmux, which might be useful to include in the README.

bind-key S command-prompt -p "tmux session name:" 'run-shell "tmuxp load %%'' -y"'

You can do an alternative with -d if you don't want to attach right away.

The message [Loading] .tmuxp/session.yaml does seem to hang in the 1st window so the binding might need tweaking :thinking:

There was an original issue #56 which had some Python based solution but the link doesn't work anymore and the issue got closed as stale.