Release v 2020.12 (#60)

Released at https://pypi.org/project/python-docs-theme/2020.12/
Changelog: https://github.com/python/python-docs-theme/releases/tag/v2020.12

Author: Mariatta

setup.py

@@ -13,7 +13,7 @@
     name='python-docs-theme',
     # Version is date based as year.month[.serial], where serial is used
     # if multiple releases are needed to address build failures.
-    version='2020.1.post1',
+    version='2020.12',
     description='The Sphinx theme for the CPython docs and related projects',
     long_description=long_description,
     author='PyPA',