docs: add changelog v4.3.1

Author: kenjis

user_guide_src/source/changelogs/index.rst

@@ -12,6 +12,7 @@ See all the changes.
 .. toctree::
     :titlesonly:
 
+    v4.3.1
     v4.3.0
     v4.2.12
     v4.2.11

user_guide_src/source/changelogs/v4.3.1.rst

@@ -0,0 +1,29 @@
+Version 4.3.1
+#############
+
+Release Date: Unreleased
+
+**4.3.1 release of CodeIgniter4**
+
+.. contents::
+    :local:
+    :depth: 3
+
+BREAKING
+********
+
+Message Changes
+***************
+
+Changes
+*******
+
+Deprecations
+************
+
+Bugs Fixed
+**********
+
+See the repo's
+`CHANGELOG.md <https://github.com/codeigniter4/CodeIgniter4/blob/develop/CHANGELOG.md>`_
+for a complete list of bugs fixed.