Update deploy command to use pull request number

Author: blckmn

.github/workflows/deploy-preview.yml

@@ -67,7 +67,7 @@ jobs:
         with:
           apiToken: ${{ secrets.CLOUDFLARE_API_TOKEN }}
           accountId: ${{ secrets.CLOUDFLARE_ACCOUNT_ID }}
-          command: pages deploy dist --project-name=${{ vars.CLOUDFLARE_PROJECT_NAME }} --branch=${{ env.COMMIT_SHORT_SHA }} --commit-dirty=true
+          command: pages deploy dist --project-name=${{ vars.CLOUDFLARE_PROJECT_NAME }} --branch=PR${{ github.event.pull_request.number }} --commit-dirty=true
 
       - name: Add deployment comment
         uses: thollander/actions-comment-pull-request@v3