Formalise Django 3.1 support

Conflicts:
	wagtail/project_template/requirements.txt

README.md

@@ -56,7 +56,7 @@ _(If you are reading this on GitHub, the details here may not be indicative of t
 
 Wagtail supports:
 
-* Django 2.2.x and 3.0.x
+* Django 2.2.x, 3.0.x and 3.1.x
 * Python 3.6, 3.7 and 3.8
 * PostgreSQL, MySQL and SQLite as database backends
 

docs/getting_started/integrating_into_django.rst

@@ -5,7 +5,7 @@ Integrating Wagtail into a Django project
 
 Wagtail provides the ``wagtail start`` command and project template to get you started with a new Wagtail project as quickly as possible, but it's easy to integrate Wagtail into an existing Django project too.
 
-Wagtail is currently compatible with Django 2.2 and 3.0. First, install the ``wagtail`` package from PyPI:
+Wagtail is currently compatible with Django 2.2, 3.0 and 3.1. First, install the ``wagtail`` package from PyPI:
 
 .. code-block:: console
 

docs/releases/upgrading.rst

@@ -135,7 +135,7 @@ The compatible versions of Django and Python for each Wagtail release are:
 +-------------------+------------------------------+-----------------------------+
 | 2.9               | 2.2, 3.0                     | 3.5, 3.6, 3.7, 3.8          |
 +-------------------+------------------------------+-----------------------------+
-| 2.10              | 2.2, 3.0                     | 3.6, 3.7, 3.8               |
+| 2.10              | 2.2, 3.0, 3.1                | 3.6, 3.7, 3.8               |
 +-------------------+------------------------------+-----------------------------+
 | 2.11              | 2.2, 3.0                     | 3.6, 3.7, 3.8               |
 +-------------------+------------------------------+-----------------------------+

setup.py

@@ -107,6 +107,7 @@ https://github.com/wagtail/wagtail/.",
         'Framework :: Django',
         'Framework :: Django :: 2.2',
         'Framework :: Django :: 3.0',
+        'Framework :: Django :: 3.1',
         'Framework :: Wagtail',
         'Topic :: Internet :: WWW/HTTP :: Site Management',
     ],

wagtail/project_template/requirements.txt

@@ -1,2 +1,2 @@
-Django>=3.0,<3.1
+Django>=3.1,<3.2
 wagtail==2.11a0