fix for code scanning alert no. 30: Workflow does not contain permissions

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>
Signed-off-by: Marco Roth <marco.roth@intergga.ch>

Author: marcoroth

.github/workflows/deploy-preview.yml

@@ -13,6 +13,8 @@ jobs:
     if: github.event.action != 'closed'
     env:
       GH_TOKEN: ${{ github.token }}
+    permissions:
+      contents: read
 
     runs-on: ubicloud-standard-2
     timeout-minutes: 10