ci: Run playwright-examples on Python 3.12 as well (#1195)

Co-authored-by: Barret Schloerke <[email protected]>

Author: gadenbuie

.github/py-shiny/setup/action.yaml

@@ -4,7 +4,7 @@ inputs:
   python-version:
     description: 'Python version to use'
     required: false
-    default: "3.11"
+    default: "3.12"
 runs:
   using: "composite"
   steps:

.github/workflows/build-docs.yaml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.11"]
+        python-version: ["3.12"]
       fail-fast: false
 
     steps:

.github/workflows/pytest.yaml

@@ -85,7 +85,7 @@ jobs:
     if: github.event_name != 'release'
     strategy:
       matrix:
-        python-version: ["3.11", "3.10", "3.9", "3.8"]
+        python-version: ["3.12", "3.11", "3.10", "3.9", "3.8"]
         os: [ubuntu-latest]
       fail-fast: false
 
@@ -210,6 +210,7 @@ jobs:
     strategy:
       matrix:
         python-version:
+          - "3.12"
           - "3.11"
           - "3.10"
           - "3.9"