Add Tips section to README.md (#287)

Change 'Known Isues' to 'Tips'

This commit will change the title of the section of the README to Tips



Change Title to Generic Reference

This commit will change the title from Model-Registry-db mysql:8.3.0 to use a generic title which will reflect that pull image rate limiting is not confined to mysql:8.3.0



Change Description of Issue

This commit will change the description to use the model-registry-db container issue as an example to demonstrate image rate limiting.



Specify Error Description is an Example

This commit will expand the description of the error to show it is an example of a wider issue.

Co-authored-by: Matteo Mortari <[email protected]>

README.md

@@ -132,3 +132,19 @@ End-to-end testing is developed with Robot Framework; this higher-lever layer of
 - demonstrate *User Stories* from high level perspective
 - demonstrate coherent logical data mapping by performing the same high level capabilities, using REST API flow Vs Python client flow,
 directly checking the end results in the backend gRPC MLMD server.
+
+## Tips
+### Pull image rate limiting
+
+Ocassionally you may encounter an 'ImagePullBackOff' error when deploying the Model Registry manifests. See example below for the `model-registry-db` container. 
+
+```
+Failed to pull image “mysql:8.3.0”: rpc error: code = Unknown desc = fetching target platform image selected from image index: reading manifest sha256:f9097d95a4ba5451fff79f4110ea6d750ac17ca08840f1190a73320b84ca4c62 in docker.io/library/mysql: toomanyrequests: You have reached your pull rate limit. You may increase the limit by authenticating and upgrading: https://www.docker.com/increase-rate-limit
+```
+
+This error is triggered by the rate limits from docker.io; in this example specifically about the image `mysql:8.3.0` (the expanded reference is `docker.io/library/mysql:8.3.0`). To mitigate against this error you could [authenticate using image pull secrets](https://kubernetes.io/docs/tasks/configure-pod-container/pull-image-private-registry/) for _local development_; or replace the image used with alternative mirrored images, for instance with the following example:
+```
+manifests/kustomize/overlays/db/model-registry-db-deployment.yaml file.
+
+spec.template.spec.containers.image: public.ecr.aws/docker/library/mysql:8.3.0
+```