Automatically alphabetise antora yaml after changes

.github/workflows/alphabetise.yml

@@ -0,0 +1,42 @@
+name: Alphabetise extension list
+
+on:
+  push:
+    branches: [ main ]
+    paths:
+      - antora-playbook.yml
+  workflow_dispatch:
+
+defaults:
+  run:
+    shell: bash
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Alphabetise
+        id: alpha
+        run: |
+          yq '.content.sources |= sort_by(.url)' antora-playbook.yml > antora-playbook-sorted.yml
+          mv antora-playbook-sorted.yml antora-playbook.yml
+
+      - name: Create Pull Request
+        # Skip main in forks
+        if: "github.repository == 'quarkiverse/quarkiverse-docs' && endsWith(github.ref, '/main')"
+        run: |
+          git checkout -b alpha-${{ github.run_id }}
+          git add antora-playbook.yml
+          git commit -m "Automatic alphabetisation"
+          git push
+          gh pr create --title "Automatic alphabetisation" --fill --repo $GITHUB_REPOSITORY
+      env:
+        GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+