Template: Add robots meta-tag, set noindex on staging

Stolen from https://github.com/dereckcurry/hugo-robots-meta-tags

.forgejo/workflows/deploy.yaml

@@ -35,6 +35,8 @@ jobs:
         if: github.ref_name != 'main'
         run: |
           sed -i "s#baseURL = 'https://hamburg.ccc.de/'#baseURL = 'https://staging.hamburg.ccc.de/pr${{ github.event.pull_request.number }}/'#" hugo.toml
+          sed -i "s#index = true#index = false#" hugo.toml
+          sed -i "s#follow = true#follow = false#" hugo.toml
       - name: Build website
         run: |
           ./fetch-calendar.sh