Add support for Python 3.10

Author: hugovk

.github/workflows/tests.yml

@@ -16,7 +16,7 @@ jobs:
 
     strategy:
       matrix:
-        python-version: ["3.7", "3.8", "3.9"]
+        python-version: ["3.7", "3.8", "3.9", "3.10-dev"]
 
     steps:
       - uses: actions/checkout@v2

setup.py

@@ -7,7 +7,7 @@
       py_modules=['cycler'],
       description='Composable style cycles',
       url='https://github.com/matplotlib/cycler',
-      platforms='Cross platform (Linux, Mac OSX, Windows)',
+      platforms='Cross platform (Linux, macOS, Windows)',
       license="BSD",
       python_requires='>=3.7',
       classifiers=['License :: OSI Approved :: BSD License',
@@ -16,6 +16,7 @@
                    'Programming Language :: Python :: 3.7',
                    'Programming Language :: Python :: 3.8',
                    'Programming Language :: Python :: 3.9',
+                   'Programming Language :: Python :: 3.10',
                    'Programming Language :: Python :: 3 :: Only',
                    ],
       keywords='cycle kwargs',