Fixed #29 -- Add Django :: 3.1 classifier. (#30)

Author: felixxm

trove_classifiers/__init__.py

@@ -86,6 +86,7 @@
     "Framework :: Django :: 2.1",
     "Framework :: Django :: 2.2",
     "Framework :: Django :: 3.0",
+    "Framework :: Django :: 3.1",
     "Framework :: Django CMS",
     "Framework :: Django CMS :: 3.4",
     "Framework :: Django CMS :: 3.5",