ci: add backports workflow

Author: mnaser

.github/workflows/backports.yaml

@@ -33,6 +33,7 @@ jobs:
       - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
         with:
           token: ${{ secrets.VEXXHOST_BOT_PAT }}
+          repository: vexxhost-bot/${{ github.event.repository.name }}
       - uses: korthout/backport-action@d07416681cab29bf2661702f925f020aaa962997 # v3.4.1
         with:
           github_token: ${{ secrets.VEXXHOST_BOT_PAT }}