Enable testing with Python 3.11

We should add Python 3.11 to our testing matrix in order to antecipate possible problems (even if we don't attempt to solve any of them right away).

Author: nicoddemus

.github/workflows/main.yml

@@ -37,13 +37,15 @@ jobs:
           "windows-py38",
           "windows-py39",
           "windows-py310",
+          "windows-py311",
 
           "ubuntu-py37",
           "ubuntu-py37-pluggy",
           "ubuntu-py37-freeze",
           "ubuntu-py38",
           "ubuntu-py39",
           "ubuntu-py310",
+          "ubuntu-py311",
           "ubuntu-pypy3",
 
           "macos-py37",
@@ -76,6 +78,10 @@ jobs:
             python: "3.10.1"
             os: windows-latest
             tox_env: "py310-xdist"
+          - name: "windows-py311"
+            python: "3.11"
+            os: windows-latest
+            tox_env: "py311"
 
           - name: "ubuntu-py37"
             python: "3.7"
@@ -102,6 +108,10 @@ jobs:
             python: "3.10.1"
             os: ubuntu-latest
             tox_env: "py310-xdist"
+          - name: "ubuntu-py311"
+            python: "3.11"
+            os: ubuntu-latest
+            tox_env: "py311"
           - name: "ubuntu-pypy3"
             python: "pypy-3.7"
             os: ubuntu-latest