Extend why running Docker containers as root is a bad idea

[michmx]

In episode 5, one of the boxes mentions "Don’t run as root" and briefly says it is a bad idea:
https://hsf-training.github.io/hsf-training-docker/05-dockerfiles/index.html#dont-run-as-root

Would be useful to provide links for the people interested on learn why it is a bad idea and security practices in general.

• Here is a suggestion with a nice description of good practices in security:
  https://sysdig.com/blog/dockerfile-best-practices/

• Information in the Docker docs is also available (but much more technical and full of jargon):
  https://docs.docker.com/engine/security/

[welcome]

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[stale]

This issue or pull request has been automatically marked as stale because it has not had recent activity. Please manually close it, if it is no longer relevant, or ask for help or support to help getting it unstuck. Let me bring this to the attention of @klieret @wdconinc @michmx for now.