Update pypi classifiers to include Wagtail, Django and audience

Author: marteinn

setup.py

@@ -51,12 +51,20 @@
     classifiers=[
         "Development Status :: 5 - Production/Stable",
         "License :: OSI Approved :: MIT License",
+        "Intended Audience :: Developers",
+        "Operating System :: OS Independent",
         "Programming Language :: Python :: 3",
         "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: Implementation :: CPython",
         "Programming Language :: Python :: Implementation :: PyPy",
+        "Framework :: Django",
+        "Framework :: Django :: 2.2",
+        "Framework :: Django :: 3.1",
+        "Framework :: Django :: 3.2",
+        "Framework :: Wagtail",
     ],
     zip_safe=False,
 )