Document the NodeFeatureRule samples and move them under deployment dir

docs/usage/custom-resources.md

@@ -86,6 +86,16 @@ See the
 [Customization guide](customization-guide.md#node-feature-rule-custom-resource)
 for full documentation of the NodeFeatureRule resource and its usage.
 
+The
+[`deployment/nodefeaturerule/samples/`](https://raw.githubusercontent.com/kubernetes-sigs/node-feature-discovery/{{site.release}}/deployment/nodefeaturerule/samples/)
+directory contains sample NodeFeatureRule objects that replicate the built-in
+default feature labels generated by NFD. The sample rules can be used as a base
+to customize NFD feature labels. To use them in place of the the NFD built-in
+labels, the corresponding feature source(s) of nfd-worker should be disabled
+with the
+(`core.labelSources`)[../reference/worker-configuration-reference.md#corelabelsources])
+configuration option.
+
 ## NodeResourceTopology
 
 When run with NFD-Topology-Updater, NFD creates NodeResourceTopology objects