add depth to json

Author: lanrat

certgraph.go

@@ -127,6 +127,7 @@ func (d *DomainNode) ToMap() map[string]string {
 	m["id"] = d.Domain
 	m["status"] = d.Status.String()
 	m["root"] = strconv.FormatBool(d.Root)
+	m["depth"] = d.Depth
 	return m
 }