Use epiforecasts-workflows app token in render_readme workflow

Update render_readme.yml to use app token so PRs created by this workflow
trigger CI checks. The default GITHUB_TOKEN doesn't trigger workflows.

Co-Authored-By: sbfnk-bot <[email protected]>

Author: sbfnk

.github/workflows/render_readme.yml

@@ -41,8 +41,17 @@ jobs:
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
     steps:
+      - name: Generate token
+        id: generate_token
+        uses: tibdex/github-app-token@v2
+        with:
+          app_id: ${{ secrets.APP_ID }}
+          private_key: ${{ secrets.APP_PRIVATE_KEY }}
+
       - name: Checkout repos
         uses: actions/checkout@v6
+        with:
+          token: ${{ steps.generate_token.outputs.token }}
 
       - name: Setup R
         uses: r-lib/actions/setup-r@v2
@@ -97,4 +106,4 @@ jobs:
           add-paths: |
             README.Rmd
             README.md
-          token: ${{ secrets.GITHUB_TOKEN }}
+          token: ${{ steps.generate_token.outputs.token }}