[TASK] Add information of removal of global extensions (#333)

Related: https://docs.typo3.org/c/typo3/cms-core/main/en-us/Changelog/12.0/Breaking-96982-RemovedSupportForGlobalExtensions.html
Releases: main

Documentation/Major/PreupgradeTasks/ConvertGlobalExtensions.rst.txt

@@ -3,7 +3,11 @@
 
 .. _convert_global_extensions:
 
-If you use global extensions, convert them to local ones.
+..  todo: Remove this chapter for TYPO3 v13
+
+..  versionchanged:: 12.0
+    The support of global extensions was removed with TYPO3 v12.0. Convert them
+    to local ones.
 
 Global extensions used to be saved in folders inside
 :file:`typo3/ext/`, such as :file:`typo3/ext/news`. In current
@@ -12,19 +16,18 @@ use local extensions below :file:`typo3conf/ext/`.
 
 To convert a global extension to a local one, do the following:
 
-* Go to the Extension Manager.
-* Uninstall the global extension.
-* Delete the files of the extension from :file:`typo3/ext/`, including
-  the directory of that extension itself.
-* Reinstall the extension from TER, which will put it into
-  :file:`typo3conf/ext/`.
-
-
-.. note::
-
-   In earlier versions of TYPO3 global extensions were an easy way of sharing
-   extensions between multiple TYPO3 instances. Nowadays the recommended way of
-   installing and maintaining extensions is via composer, where you may use
-   different strategies to achieve the same goal. One example would be to use
-   `"path repositories" <https://getcomposer.org/doc/05-repositories.md#path>`__
-   in your composer.json file
+*   Go to the :guilabel:`Admin Tools > Extensions` backend module.
+*   Uninstall the global extension.
+*   Delete the files of the extension from :file:`typo3/ext/`, including
+    the directory of that extension itself.
+*   Reinstall the extension from the TYPO3 Extension Repository, which will put
+    it into :file:`typo3conf/ext/`.
+
+
+..  note::
+    In earlier versions of TYPO3 global extensions were an easy way of sharing
+    extensions between multiple TYPO3 instances. Nowadays, the recommended way of
+    installing and maintaining extensions is via Composer, where you may use
+    different strategies to achieve the same goal. One example would be to use
+    `"path repositories" <https://getcomposer.org/doc/05-repositories.md#path>`__
+    in your :file:`composer.json` file