docs: add docs

Author: kenjis

user_guide_src/source/changelogs/v4.5.4.rst

@@ -30,6 +30,8 @@ Deprecations
 Bugs Fixed
 **********
 
+- **Routing:** Fixed a bug that filters passed to `$routes->group()` were not merged
+  into filters passed to the inner routes.
 - **CURLRequest:** Fixed a bug preventing the use of strings for ``version`` in the config array
   when making requests.
 

user_guide_src/source/incoming/routing.rst

@@ -564,6 +564,9 @@ run the filter before or after the controller. This is especially handy during a
 
 The value for the filter must match one of the aliases defined within **app/Config/Filters.php**.
 
+.. note:: Prior to v4.5.4, due to a bug, filters passed to the ``group()`` were
+    not merged into the filters passed to the inner routes.
+
 Setting Other Options
 =====================