Add PR auto-merge step to preview workflow

Author: andrey-helldar

.github/workflows/preview.yml

@@ -19,6 +19,13 @@ jobs:
                     fetch-depth: 0
 
             -   name: Update Previews
+                id: preview
                 uses: ./
                 with:
                     token: ${{ secrets.GITHUB_TOKEN || env.GITHUB_TOKEN }}
+
+            -   name: Merge PR
+                if: steps.preview.outputs.pullRequestNumber != ''
+                env:
+                    GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+                run: gh pr merge --merge --delete-branch ${{ steps.preview.outputs.pullRequestNumber }}