fix: clarify the gax-nodejs usage in README (#1352) (#528)

Co-authored-by: Benjamin E. Coe <bencoe@google.com>
Co-authored-by: Jeffrey Rennie <rennie@google.com>
Source-Link: googleapis/synthtool@e1557e4
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-nodejs:latest@sha256:c2641f0628c1077d504eca6b065517b0cc54336f09a9a38e3614c4b412dd9d37

Author: 3 people

.github/.OwlBot.lock.yaml

@@ -13,5 +13,5 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-nodejs:latest
-  digest: sha256:f74e740638e66be7ced1540626217dbb72980eb73885b2339a70592f38c9ff2c
-# created: 2022-04-06T18:36:33.987617127Z
+  digest: sha256:c2641f0628c1077d504eca6b065517b0cc54336f09a9a38e3614c4b412dd9d37
+# created: 2022-04-07T16:48:24.139011696Z

README.md

@@ -94,6 +94,9 @@ To run commands against the clusters created, you will need to use the
 (and the associated kubectl command-line interface).
 
 
+
+This library is built on top of google-gax as its transport layer. To customize the common behavior of this client library (timeout, retry, etc), see [Client Library Howto](https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md).
+
 ## Samples
 
 Samples are in the [`samples/`](https://github.com/googleapis/nodejs-cloud-container/tree/main/samples) directory. Each sample's `README.md` has instructions for running its sample.