tmux:TODO: Display when pane is in fullscreen mode

Sometimes I forget that I maximized a pane as there is no visual
indicator.

.config/tmux/tmux.conf

@@ -188,6 +188,7 @@ if -F "#{<:#{version},3.2}" {
 	set -g pane-active-border-style "#{?pane_in_mode,bg=#{@accent_color}#,fg=#{@ui_color},#{?synchronize-panes,fg=#{@sync_color},fg=#{@accent_color}}}"
 }
 
+# TODO: display when pane is in fullscreen mode
 # Display in the status bar when the prefix was pressed, copy-mode is active, or
 # `synchronize-panes` is turned on
 set -g @prefix_highlight_fg '#{@accent_color}'