Added stub release notes for 3.1.5.

docs/releases/3.1.5.txt

@@ -0,0 +1,12 @@
+==========================
+Django 3.1.5 release notes
+==========================
+
+*Expected January 4, 2021*
+
+Django 3.1.5 fixes several bugs in 3.1.4.
+
+Bugfixes
+========
+
+* ...

docs/releases/index.txt

@@ -32,6 +32,7 @@ versions of the documentation contain the release notes for any later releases.
 .. toctree::
    :maxdepth: 1
 
+   3.1.5
    3.1.4
    3.1.3
    3.1.2