build: Add tox rules and update ci matrix.

Tox did not have the other python versions so we couldn't test locally
with those easily.  Also, we don't need to run the `docs`, `quality` and
`pii_check` on all versions. Running it on the latest version is
sufficient.

.github/workflows/ci.yml

@@ -14,9 +14,20 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-20.04]
+        os: [ 'ubuntu-20.04' ]
         python-version: ['3.8', '3.11', '3.12']
-        toxenv: [quality, docs, pii_check, django42]
+        toxenv: [ 'django42' ]
+        # Only run these other workflows on the latest python version we support.
+        include:
+          - python-version: '3.12'
+            toxenv: 'quality'
+            os: 'ubuntu-20.04'
+          - python-version: '3.12'
+            toxenv: 'docs'
+            os: 'ubuntu-20.04'
+          - python-version: '3.12'
+            toxenv: 'pii_check'
+            os: 'ubuntu-20.04'
 
     steps:
     - uses: actions/checkout@v4

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py{38}-django{42}, quality, docs, pii_check
+envlist = py{38,311,312}-django{42}, quality, docs, pii_check
 
 [doc8]
 ignore = D001