add registration file support

README.md

@@ -5,6 +5,7 @@
 - `/var/lib/matrix-synapse/signing/`
 - `/var/lib/matrix-synapse/uploads/`
 - `/etc/ssl/matrix-synapse/:ro`: certificates have to be here
+- `/var/lib/matrix-synapse/registrations/`
 
 # Environment Variables
 ## SERVER_NAME
@@ -63,6 +64,11 @@ Whether to generate new thumbnails on the fly to precisely match the resolution
 ## REPORT_STATS
 - default: no
 
+## REGISTRATIONS
+- default: []
+
+Comma seperated list of registration files to load.
+
 Whether to report statistics.
 
 # Ports