feat: Cloudflare Pages preview deployments (#18)

Backported from #17

Author: jasonad123

.github/workflows/pkgdown.yaml

@@ -22,6 +22,8 @@ jobs:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
     permissions:
       contents: write
+      deployments: write
+      pull-requests: write
     steps:
       - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
 
@@ -40,10 +42,32 @@ jobs:
         run: pkgdown::build_site_github_pages(new_process = FALSE, install = FALSE)
         shell: Rscript {0}
 
-      - name: Deploy to GitHub pages 🚀
+      - name: Deploy to GitHub pages (backup)
         if: github.event_name != 'pull_request'
         uses: JamesIves/github-pages-deploy-action@9d877eea73427180ae43cf98e8914934fe157a1a # v4.7.6
         with:
           clean: false
           branch: gh-pages
           folder: docs
+
+      - name: Deploy to Cloudflare Pages
+        if: github.event_name == 'pull_request'
+        uses: cloudflare/wrangler-action@v3
+        id: cloudflare
+        with:
+          apiToken: ${{ secrets.CLOUDFLARE_API_TOKEN }}
+          accountId: ${{ secrets.CLOUDFLARE_ACCOUNT_ID }}
+          command: pages deploy docs --project-name=mobdb --branch=${{ github.head_ref || github.ref_name }} --commit-dirty=true
+          gitHubToken: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Comment preview URL on PR
+        if: github.event_name == 'pull_request'
+        uses: actions/github-script@v7
+        with:
+          script: |
+            github.rest.issues.createComment({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body: `## Preview Deployment\n\n:rocket: Preview URL: ${{ steps.cloudflare.outputs.deployment-url }}\n\nBranch alias: ${{ steps.cloudflare.outputs.pages-deployment-alias-url }}`
+            })