feat: added seldon rocks to scan workflow (#28)

Adding ROCKs to weekly CVE scan is part of ROCK delivery.
Details are in canonical/seldon-core-operator#133

Summary of changes:

Added Seldon ROCKs to weekly scan.

.github/workflows/build_and_scan_rocks.yaml

@@ -14,6 +14,10 @@ jobs:
     strategy:
       matrix:
         rock:
+          - mlserver-huggingface
+          - mlserver-mlflow
+          - mlserver-sklearn
+          - mlserver-xgboost
           - seldon-core-operator
           - sklearnserver
     uses: canonical/charmed-kubeflow-workflows/.github/workflows/build_and_scan_rock.yaml@main