ci: add co-author info from issue author in auto-generated PRs

Author: x0rw

.github/workflows/auto-pr-on-issue.yml

@@ -38,7 +38,11 @@ jobs:
       - name: Create Pull Request
         uses: peter-evans/create-pull-request@v6
         with:
-          commit-message: "Add guideline for issue #${{ github.event.issue.number }}"
+          commit-message: |
+            Add guideline for issue #${{ github.event.issue.number }}
+
+            Co-authored-by: ${{ github.event.issue.user.login }} <${{ github.event.issue.user.login }}@users.noreply.github.com>
+
           branch: guideline-${{ github.event.issue.number }}
           title: "[auto-pr] #${{ github.event.issue.number }}: ${{ github.event.issue.title }}"
           body: |