Begin work toward CI

Author: pjkundert

.github/workflows/main.yml

@@ -19,7 +19,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [2.7, 3.5, 3.6, 3.7, 3.8, 3.9, 3.x, pypy3]
+        python-version: [3.9, 3.10, 3.11, 3.12, 3.x, pypy3]
 
     steps:
     - uses: actions/checkout@v2