Parameterize base image

[gbraad]

... to allow

• use newer versions
• Add bootc-based images #65
• use customized base images

Ref: gbraad/dotfiles#44

[gbraad]

Using parameterized container builds have already been done for httpw://github.com/gbraad-homelab/. This should be easily to duplicate.

[gbraad]

At the moment, the image version, eg. 41 is still everywhere. Updating this would be a 'nightware', so this needs to be a variable inside the workflows.