Enhancement: Allow setting window flags characters

### Describe the feature you'd like
A way to set the window flag characters.
E.g. 🔍 if a window is zoomed (instead of Z) etc.

### Describe alternatives you've considered
I tried setting `set-option -g window-status-current-format '#I:#W#{?window_zoomed_flag, 🔍 ,}'`
but this doesn't work as dracula overrides it.