add kind to the step template

Author: danielperezz

cli/utils/step_item_template.yaml.j2

@@ -14,4 +14,5 @@ spec:
   filename: {{ filename|default('') }}              {# Implementation file #}
   image: mlrun/mlrun                                {# Base image name #}
   requirements: []                                  {# List of Pythonic library requirements #}
+  kind: ''                                          {# Step kind #}
 version: 1.0.0                                      {# Step version, should follow standard semantic versioning schema #}