HowToAddTranslation: Settings.cfg must be replaced by guides.xml (#516)

* HowToAddTranslation: Settings.cfg must be replaced by guides.xml

Settings.cfg cannot be used anymore.

* [TASK] Language checks

---------

Co-authored-by: Sarah McCarthy <sarahmccarthy123@yahoo.com>

Author: franzholz

Documentation/Advanced/HowToAddTranslation.rst

@@ -32,10 +32,10 @@ wind up on the corresponding translated page.
          Documentation
          └──  Localization.de_DE
               ├── Index.rst
-              └── Settings.cfg
+              └── guides.xml
 
 
-#. Update the file :ref:`settings-cfg`.
+#. Update the file `Documentation/guides.xml <https://docs.typo3.org/permalink/h2document:settings-guides-xml>`_.
 
 #. Translate the texts