Add short note about image locations

[adwk67]

For users that are considering using custom images based on our own images, it may be useful to have a short explanation as to where to find them i.e. in this.

### Tasks
- [x] update the product image selection page to better explain where to find base images for custom images: https://github.com/stackabletech/documentation/pull/567
- [x] link from the "Supported versions" page to product image selection/custom images: https://github.com/stackabletech/documentation/pull/569

### Update 'Supported versions' section in product operator docs
- [ ] https://github.com/stackabletech/airflow-operator/pull/413
- [ ] https://github.com/stackabletech/druid-operator/pull/540
- [ ] https://github.com/stackabletech/hbase-operator/pull/481
- [ ] https://github.com/stackabletech/hdfs-operator/pull/507
- [ ] https://github.com/stackabletech/hive-operator/pull/442
- [ ] https://github.com/stackabletech/kafka-operator/pull/687
- [ ] https://github.com/stackabletech/nifi-operator/pull/596
- [ ] https://github.com/stackabletech/spark-k8s-operator/pull/376
- [ ] https://github.com/stackabletech/superset-operator/pull/478
- [ ] https://github.com/stackabletech/trino-operator/pull/567
- [ ] https://github.com/stackabletech/zookeeper-operator/pull/796
- [ ] https://github.com/stackabletech/opa-operator/pull/548

[fhennig]

I think I would like to instead add a tutorial: How to run customized product images

This tutorial should:

• explain where all the images are
• show how to use our images as base images
• show how to use this custom image in a Stacklet definition

maybe spark can be a good Stacklet to try this on, with adding some custom jar to it.

I would also link to the tutorial from here and link back to this page as well.

In the Supported versions section of the operators we can also link to the product image selection page, that should then send people on the right track.

opinions @lfrancke @adwk67 ?

Edit: the 'custom images' section in the product image selection docs could also link to where the base images can be found.

[lfrancke]

Yes. A tutorial for this would be a great idea.

[adwk67]

Yes, I agree. That makes a lot of sense.

[fhennig]

Alright, so I've created a different ticket for the tutorial: #568

And for this one I simply want to link from the oeprators to the product image selection page, and update that page to more clearly explain where the base images are.

[fhennig]

all the task lists are done