Add completions

[tony]

https://click.palletsprojects.com/en/7.x/bashcomplete/

Add autocompletion= for load/freeze/etc.

eval "$(_TMUXP_COMPLETE=source_zsh tmuxp)"

[craigforr]

It may just be me, but when I attempt to load a session with the following command line, it fails to complete the path -- directories or filename:

tmuxp load ~/.tmuxp/session<TAB><TAB>

This is the case whether tmuxp completion is loaded or not. Am I perhaps missing some configuration, or is this behavior expected?