Add support for docutils==0.20.x (#1517)

Closes #1516

Author: humitos

setup.cfg

@@ -46,7 +46,7 @@ packages = sphinx_rtd_theme
 python_requires = >=3.6
 install_requires = 
 	sphinx >=5,<8
-	docutils <0.19
+	docutils <0.21
 	sphinxcontrib-jquery >=4,<5
 tests_require = 
 	pytest