Replace mysql examples with mariadb

[BretFisher]

The mysql image doesn't have the same tools it used to have in my videos. Replace with the official mariadb image in the lectures and code. mariadb is a MySQL fork and should be a plug-and-play replacement.

https://hub.docker.com/_/mariadb

Lecture's to replace or precede with info

• Lecture added before the Assignment
• 22. Assignment: Manage Multiple Containers
• Getting a shell inside containers uses a MySQL image for various commands, or replace with video showing microdnf update && microdnf install -y procps to support ps aux
• compose-sample-1/compose-2.yml
• compose-sample-1/compose-3.yml (replace percona with updated solution)
• there may be more. I mention MySQL a lot in the course.

Original Q&A (one of many)