docs: add changelog and upgrade note

Author: kenjis

user_guide_src/source/changelogs/v4.4.0.rst

@@ -144,6 +144,8 @@ Changes
   So if you installed CodeIgniter under the folder that contains the special
   characters like ``(``, ``)``, etc., CodeIgniter didn't work. Since v4.4.0,
   this restriction has been removed.
+- **RouteCollection:** The array structure of the protected property ``$routes``
+  has been modified for performance.
 
 Deprecations
 ************

user_guide_src/source/installation/upgrade_440.rst

@@ -66,6 +66,15 @@ Interface Changes
 Some interface changes have been made. Classes that implement them should update
 their APIs to reflect the changes. See :ref:`v440-interface-changes` for details.
 
+RouteCollection::$routes
+========================
+
+The array structure of the protected property ``$routes`` has been modified for
+performance.
+
+If you extend ``RouteCollection`` and use the ``$routes``, update your code to
+match the new array structure.
+
 Mandatory File Changes
 **********************