Enhancement: support different colors of active/inactive panes

[ericfengchao]

Describe the feature you'd like

support different colors of active/inactive panes. something like this

[ethancedwards8]

If you can find an existing implementation, please share it. I'll be happy to implement this.

[o0th]

It should be easy to achieve, something like

set -g window-style 'fg=#f8f8f2,bg=##44475a'
set -g window-active-style 'fg=#f8f8f2,bg=#282a36'