Support Python 3.11

This adds support for targetting Python 3.11 via picking up the
latest grammar from parso while also validating support for running
on 3.11 by adding it to the CI matrix.

.github/workflows/ci.yml

@@ -7,8 +7,8 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-20.04, windows-2019]
-        python-version: ["3.10", "3.9", "3.8", "3.7", "3.6"]
-        environment: ['3.8', '3.10', '3.9', '3.7', '3.6', 'interpreter']
+        python-version: ["3.11", "3.10", "3.9", "3.8", "3.7", "3.6"]
+        environment: ['3.8', '3.11', '3.10', '3.9', '3.7', '3.6', 'interpreter']
     steps:
       - name: Checkout code
         uses: actions/checkout@v2