rbac-lookup: add page (#3165)

pages/common/rbac-lookup.md

@@ -0,0 +1,24 @@
+# rbac-lookup
+
+> Find roles and cluster roles attached to any user, service account or group name in your Kubernetes cluster.
+> More information: <https://github.com/reactiveops/rbac-lookup>.
+
+- View all RBAC bindings:
+
+`rbac-lookup`
+
+- View RBAC bindings that match a given expression:
+
+`rbac-lookup {{search_term}}`
+
+- View all RBAC bindings along with the source role binding:
+
+`rbac-lookup -o wide`
+
+- View all RBAC bindings filtered by subject:
+
+`rbac-lookup -k {{user|group|serviceaccount}}`
+
+- View all RBAC bindings along with IAM roles (if you are using GKE):
+
+`rbac-lookup --gke`