update README

Author: mevdschee

README.md

@@ -642,6 +642,7 @@ You can tune the middleware behavior using middleware specific configuration par
 - "dbAuth.usernameColumn": The users table column that holds usernames ("username")
 - "dbAuth.passwordColumn": The users table column that holds passwords ("password")
 - "dbAuth.returnedColumns": The columns returned on successful login, empty means 'all' ("")
+- "dbAuth.registerUser": JSON user data (or "1") in case you want the /register endpoint enabled ("")
 - "dbAuth.sessionName": The name of the PHP session that is started ("")
 - "jwtAuth.mode": Set to "optional" if you want to allow anonymous access ("required")
 - "jwtAuth.header": Name of the header containing the JWT token ("X-Authorization")