Document synchronize-panes auto-hide feature in CONFIG.md

Author: webdavis

docs/CONFIG.md

@@ -812,6 +812,13 @@ set -g @dracula-synchronize-panes-label "Sync"
 
 `set -g @dracula-refresh-rate 5` affects this widget
 
+Set the following variable to auto-hide this label when sync is `off`:
+
+```bash
+set -g @dracula-synchronize-panes-auto-hide true  # Defaults to 'false'
+set -g @dracula-synchronize-panes-refresh-rate "0.5"  # Defaults to no value
+```
+
 ### sys-temp - [up](#table-of-contents)
 
 This widget displays the system temperature.