OWNERS: Document 'component' property

Example of OpenShift components:

  $ curl -sH Accept:application/json -H Content-Type:application/json --data '{"jsonrpc":"2.0","method":"SelectizeJS.list_components","id":1,"params":[{"term":"..","descrs":1,"disabled":0,"product":"v314_product"}]}' https://bugzilla.redhat.com/jsonrpc.cgi | jq -r '[.result[].value] | sort[]'
  Build
  Cincinnati
  Cloud Compute
  Cloud Credential Operator
  Cluster Loader
  Cluster Version Operator
  Compliance Operator
  ...

Based on Scott's [1]:

> It's used downstream to facilitate mapping to BZ Components.

[1]: openshift#344 (comment)

OWNERS

@@ -8,4 +8,7 @@ approvers:
   - wking
   - vrutkovs
   - jottofar
+
+# This is a Red Hat extension, mapping the Git repository to an OpenShift Bugzilla component:
+# https://bugzilla.redhat.com/enter_bug.cgi?product=OpenShift%20Container%20Platform
 component: "Cluster Version Operator"