Fix PR preview workflow: add permissions, use ubuntu-latest, update checkout action

Author: devnomadic

.github/workflows/preview.yml

@@ -8,14 +8,18 @@ on:
       - synchronize
       - closed
 
+permissions:
+  contents: write
+  pull-requests: write
+
 concurrency: preview-${{ github.ref }}
 
 jobs:
   deploy-preview:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Setup Ruby
         uses: ruby/setup-ruby@v1