Update top-level .gitignore with directory paths

Author: github-actions[bot]

.gitignore

@@ -16,6 +16,9 @@ log/*
 run/*
 local/
 
+# Written by bin/install-audio-satellite.sh when AirPlay is enabled
+bin/.install-audio-satellite-airplay
+
 # [apps] apps/access-control-webhook/.gitignore
 apps/access-control-webhook/config/.ssh/
 apps/access-control-webhook/config/hooks.json