[DOCS] Document styling of current page in fluid_styled_content menu content elements

Document https://review.typo3.org/c/Packages/TYPO3.CMS/+/73048 in the extensions manual

Resolves: #97404
Releases: main

Change-Id: If241f826fcc8972877eb9b4f6c7281a814b65ef9
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74331

Tested-by: Björn Jacob <bjoern.jacob@tritum.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Annett Jähnichen <mcmietz@web.de>
Tested-by: Jonas Eberle <flightvision@googlemail.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Lina Wolf <112@linawolf.de>
Reviewed-by: Björn Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Jonas Eberle <flightvision@googlemail.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Lina Wolf <112@linawolf.de>

typo3/sysext/fluid_styled_content/Documentation/ContentElements/Menu/Index.rst

@@ -67,3 +67,30 @@ shown.
 
 In case no pages are selected, the menu will be rendered from the
 current page where the menu is put on.
+
+Styling of the current page in a menu
+======================================
+
+.. versionadded:: 12.0
+    All menu content elements related to page navigation reflect the "current"
+    state of a page now.
+
+If the current page is displayed within a menu the aria attribute
+:html:`aria-current="page"` is added to the a-tag of a menu-item.
+
+For styling with CSS the attribute of the link can be used:
+
+.. code-block:: css
+    :caption: EXT:site_package/Public/Css/menu.css
+
+    [aria-current="page"] {
+       /* Special style for the current page link */
+    }
+    [aria-current="page"]:hover {
+       /* Special style for the current page link when hovered */
+    }
+    [aria-current="page"]::before {
+       /* Special virtual element for additions like chevrons, etc. */
+    }
+
+The default styling of contains no style for the current page.