[updatenotification] Added option to iterate over modules directory instead using modules defined in config.js, doc for MagicMirrorOrg/MagicMirror#3755 (#295)

Author: khassel

modules/updatenotification.md

@@ -33,6 +33,7 @@ The following properties can be configured:
 | `updates`                  | Array of updates modules commands. <br> **Default value:** `[]` (see bellow)                                                                                                                                                                                  |
 | `updateTimeout`            | Maximum Update duration before cancel it. <br> **Default Value:** `120000` (2 minutes)                                                                                                                                                                        |
 | `updateAutorestart`        | Restart automaticaly MagicMirror² after update is done. <br> **Default Value:** `false`                                                                                                                                                                       |
+| `useModulesFromConfig`     | If `false` iterate over modules directory instead using modules defined in `config.js`. <br> **Default Value:** `true`                                                                                                                                        |
 
 ### `updates` Array