Added stub release notes for 4.2.1.

docs/releases/4.2.1.txt

@@ -0,0 +1,12 @@
+==========================
+Django 4.2.1 release notes
+==========================
+
+*Expected May 1, 2023*
+
+Django 4.2.1 fixes several bugs in 4.2.
+
+Bugfixes
+========
+
+* ...

docs/releases/index.txt

@@ -33,6 +33,7 @@ versions of the documentation contain the release notes for any later releases.
 .. toctree::
    :maxdepth: 1
 
+   4.2.1
    4.2
 
 4.1 release