introduce setting "allowAdHocMeetings" to show or hide Adhoc-Meetings button

README.md

@@ -12,6 +12,7 @@ up but links break if the file is missing or malformed.
 | `jitsiLauncher` | Domain of this Jitsi launcher. Used for the meeting URLs created by the meeting creator (Nextcloud, adhoc link). |
 | `jitsiHost` | Jitsi domain. Used for the browser fallback URL, the desktop protocol URL and the UID of generated ICS files. |
 | `nextcloudBase` | Nextcloud instance for calendar event creation. The "Create in Nextcloud Calendar" button is only shown if this is set. |
+| `allowAdhocMeetings` | Whether adhoc meetings are allowed. The "Create Adhoc Link" button is only shown if this is `true`. |
 | `launchTimeout` | Timeout in ms before the browser fallback is shown after trying to start the jitsi-meet-electron client. |
 | `backgroundImage` | Path to the page background image. Empty: no background. |
 | `logo` | Path to the logo shown in the logo bar. Empty: logo bar stays hidden. |