List SQL backend extensions as alternatives

README.md

@@ -131,3 +131,11 @@ Add the following to your `config.php`:
             'arguments' => array('https://example.com/webdav'),
         ),
     ),
+
+
+Alternatives
+------------
+Other extensions allow connecting to external user databases directly via SQL, which may be faster:
+
+* [user_sql](https://github.com/nextcloud/user_sql)
+* [user_backend_sql_raw](https://github.com/PanCakeConnaisseur/user_backend_sql_raw)