add missing checkout step

.github/workflows/workflow.yml

@@ -13,6 +13,7 @@ jobs:
     name: Build and Publish
     runs-on: ubuntu-latest
     steps:
+      - uses: actions/checkout@v4
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v1
       - name: Login to ghcr.io