add dry run

Author: bshaffer

.github/workflows/docs.yml

@@ -8,17 +8,19 @@ on:
             tag:
                 description: 'Tag to generate documentation for'
                 required: false
+    pull_request:
 
 permissions:
   contents: write
 
 jobs:
     docs:
         name: "Generate and Deploy Documentation"
-        uses: GoogleCloudPlatform/php-tools/.github/workflows/doctum.yml@doctum
+        uses: GoogleCloudPlatform/php-tools/.github/workflows/doctum.yml@main
         with:
           title: "Google Cloud PHP Client"
           default_version: ${{ inputs.tag || github.ref_name }}
           exclude_file: aliases.php
           tag_pattern: "v2.*"
+          dry_run: ${{ github.event_name == 'pull_request' }}