Add high-level description of docker images and their build process

[VJalili]

This PR extends the website by adding documentation about the docker images, their relationship, the motivation behind building them into multiple images, and a high-level description of their build, test, and publish process.

The documentation on building, pushing, developing, and updating CI/CD for other container registries will be added in follow-up PRs.

[mwalker174]

Thank you for putting this together. The docker system has become a bit complex over the years and this adds a lot of clarity as to how the build system works.

I have a few minor suggestions and also it looks like the manual docker publishing section is missing some content.

In addition, the documentation is very technical and I think we want to make it clear that this is intended for developers and not users (who we don't want to scare away ;)). One way to do that would be place the "Docker Images" as a subsection under a "Development" or "For Developers" section. Not sure how that will look visually since there's already a few levels of subsections, so you could try to just add a clear disclaimer to the Overview.

On a related note, I think it would be helpful to have a small section under "Getting Started" about dockers that is intended for users. A quick description of where to find dockers.json and that the images there are updated with workflows and other code.

[VJalili]

Thanks for the review, @mwalker174! I implemented the suggested changes; I agree it reads better now; thank you! I would appreciate it if you could re-review it.

[mwalker174]

Thanks! Just a couple last comments but on the whole good to go.

[VJalili]

Thanks for the review, @mwalker174!