Update Github Actions to include wagtail4 tests

.github/workflows/python-tox.yml

@@ -4,6 +4,7 @@ on: [push, pull_request]
 
 jobs:
   build:
+    continue-on-error: ${{ matrix.experimental }}
     runs-on: ubuntu-latest
     services:
       postgres:
@@ -28,14 +29,25 @@ jobs:
           - {version: 3.8, tox: 38}
           - {version: 3.9, tox: 39}
           - {version: '3.10', tox: 310}
-        django: [32, 40]
-        wagtail: [215, 216, 30]
+        django: [32, 40, 41]
+        wagtail: [215, 216, 30, 40]
         factoryboy: [32]
+        experimental: [false]
+        include:
+          - python-version: {version: '3.10', tox: 310}
+          - django: 41
+          - wagtail: 'main'
+          - factoryboy: [32]
+          - experimental: true
         exclude:
           - wagtail: 215
             django: 40
+          - wagtail: 215
+            django: 41
           - python-version: {version: 3.7, tox: 37}
             django: 40
+          - python-version: {version: 3.7, tox: 37}
+            django: 41
 
     steps:
     - uses: actions/checkout@v1