Migration: consider lessons that are FULLLY Jekyll

[zkamvar]

the HPC intro repository extensively uses snippets and custom configuration to make the HPC lessons work across university HPC systems.

Snippets in Jekyll are similar to child documents in RMarkdown, they can contain separate pieces of information in markdown format that can be used to tweak the presentation of the lesson.

Moreover, these lessons are some that heavily use custom values in the _config.yaml files. I don't want to put them in a situation where they are unable to use these values.