[TASK] Display webhooks manual in the main menu (#296)

* [TASK] Display webhooks manual in the main menu

* [TASK] Display webhooks manual in the main menu

* [TASK] Display webhooks manual in the main menu

Author: linawolf

Documentation/_mainMenu.rst.txt

@@ -193,6 +193,12 @@
 
         *   :doc:`12.4 <typo3/cms-t3editor/12:Index>`
 
+    *   :doc:`webhooks <typo3/cms-webhooks/13:Index>`
+
+        *   :doc:`13.4 <typo3/cms-webhooks/main:Index>`
+        *   :doc:`12.4 <typo3/cms-webhooks/12:Index>`
+        *   :doc:`14-dev <typo3/cms-webhooks/main:Index>`
+
     *   :doc:`workspaces <typo3/cms-workspaces:Index>`
 
         *   :doc:`13.4 <typo3/cms-workspaces/13:Index>`