feat: add ci to verify docker build is reliable

[devstein]

Description

We want new users to be able to reliably build the Sparkmagic example Docker images. Right now, we have no integration tests using the Docker images, so the only failures are reported by users.

This adds CI to ensure the Docker image always builds. In the future, we can add CI to actually run the images and run integration tests against it.

Relates to #789 and #791

Checklist

• Wrote a description of my changes above
• Formatted my code with black
• Added a bullet point for my changes to the top of the CHANGELOG.md file
• Added or modified unit tests to reflect my changes
• Manually tested with a notebook
• If adding a feature, there is an example notebook and/or documentation in the README.md file