docs: AAQ default namespace selector

Signed-off-by: Itamar Holder <iholder@redhat.com>

docs/cluster-configuration.md

@@ -1166,6 +1166,14 @@ spec:
         some-label: "some value"
     allowApplicationAwareClusterResourceQuota: true
 ```
+
+**Note**: if a namespace selector is not being defined, AAQ would target namespaces with the `application-aware-quota/enable` key.
+It is also possible to target every namespace by defining an empty (non-nil) namespaceSelector as follows:
+```yaml
+spec:
+  applicationAwareConfig:
+    namespaceSelector: {}
+```
 ## Configure higher workload density
 Cluster administrators can opt-in for higher VM workload density by configuring the memroy overcommit percentage as follows:
 ```yaml