Added stub release notes for 3.1.7.

docs/releases/3.1.7.txt

@@ -0,0 +1,12 @@
+==========================
+Django 3.1.7 release notes
+==========================
+
+*Expected March 1, 2021*
+
+Django 3.1.7 fixes several bugs in 3.1.6.
+
+Bugfixes
+========
+
+* ...

docs/releases/index.txt

@@ -39,6 +39,7 @@ versions of the documentation contain the release notes for any later releases.
 .. toctree::
    :maxdepth: 1
 
+   3.1.7
    3.1.6
    3.1.5
    3.1.4