DEP: Add Python 3.10 support (#6)

Author: snowman2

.github/workflows/tests.yaml

@@ -24,7 +24,7 @@ jobs:
       fail-fast: true
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        python-version: [3.8, 3.9]  # '3.10'
+        python-version: ['3.8', '3.9', '3.10']
 
     steps:
       - uses: actions/checkout@v2

setup.cfg

@@ -17,6 +17,7 @@ classifiers =
     Programming Language :: Python
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
+    Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3
     Topic :: Software Development :: Libraries :: Python Modules
     Topic :: Scientific/Engineering :: GIS