chore: Replace personal access token with GitHub App Token (#24)

Author: Reikyo

.github/workflows/create-dataset-site-template-pr.yaml

@@ -31,13 +31,20 @@ jobs:
         # git stashing if no material changes allows the next step to close the PR if one is already open
         run: if [ "$(git diff --numstat | grep -vc '^1\s.*datasetsite\.mustache\|1\s.*datasetsite-csp\.mustache\|.*datasetsite-csp\.static\.zip$')" -eq "0" ]; then git stash; else echo "Material changes found"; fi
         working-directory: ./
-        
+
+      - name: Generate GitHub App Token
+        uses: actions/create-github-app-token@v1
+        id: generate-token
+        with:
+          app-id: ${{ secrets.GH_APP_ID }}
+          private-key: ${{ secrets.GH_APP_PRIVATE_KEY }}
+
       - name: Create Pull Request
         id: cpr
         uses: peter-evans/create-pull-request@v7
         with:
           path: ./
-          token: ${{ secrets.PUBLIC_REPO_ACCESS_TOKEN }}
+          token: ${{ steps.generate-token.outputs.token }}
           commit-message: Update dataset site template
           committer: openactive-bot <openactive-bot@users.noreply.github.com>
           author: openactive-bot <openactive-bot@users.noreply.github.com>