Fix small typo in README.md

README.md

@@ -30,7 +30,7 @@ E.g. a configuration file for MySQL can be configured like this:
 {
   backupninja: {
     configs: {
-      10-localhost.mysql: {
+      '10-localhost.mysql': {
         databases: 'all',
         dbusername: 'backupninja',
         dbpassword: 'secretpass',