Fix Powerline docs on what options it supports
Fix Powerline docs on what options it supports

When the path rework landed, I missed this bit of documentation. The
Powerline theme, since it is a clone of the Powerline project, only
supports specific sections. The current working directory is one of
them, but there are a lot of config options for that feature. They need
to be listed here as options that are respected.

pkkolos/liquidprompt,jaesivsm/liquidprompt,laurentbardin/liquidprompt,nojhan/liquidprompt,milouse/liquidprompt