Add Python 3.10 CI target

Author: fantix

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [ '3.6', '3.7', '3.8', '3.9' ]
+        python-version: [ '3.6', '3.7', '3.8', '3.9', '3.10' ]
     steps:
       - name: source code
         uses: actions/checkout@v2
@@ -117,7 +117,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [ '3.6', '3.7', '3.8', '3.9' ]
+        python-version: [ '3.6', '3.7', '3.8', '3.9', '3.10' ]
     services:
       postgres:
         image: fantix/postgres-ssl:13.1