Add classifier for python 3.10
This is so the version shield ( [![PyPI](https://img.shields.io/pypi/pyversions/rdflib.svg)](https://pypi.python.org/pypi/rdflib) ) shows up correctly in future releases.
@@ -71,6 +71,7 @@ setup(
"Programming Language :: Python :: 3.7",
"Programming Language :: Python :: 3.8",
"Programming Language :: Python :: 3.9",
+ "Programming Language :: Python :: 3.10",
"License :: OSI Approved :: BSD License",
"Topic :: Software Development :: Libraries :: Python Modules",
"Operating System :: OS Independent",
