Consistent styles on suggested teaching demos page (hold until new checkout process launches)

There are a variety of style inconsistencies that should be cleaned up in the [suggested demo episodes](https://preview.carpentries.org/instructor-training/demo_lessons.html). However, there is a high chance this page will be overhauled when the revised checkout process launches, allowing trainees to choose their own episodes.

Thus while these could be updated now, it's easier to hold for now.

Here is a (hopefully-exhaustive) list of inconsistencies - feel free to add:

- Capitalization at the start of non-linked table cells is mostly lower-case but occasionally sentence case
- Most lists of episodes are formatted with `*` but some are just lines of text (could also be converted to MD list with `-`)
- Some listed episodes (in good starting points) are not linked
- Some inconsistencies in use of period to end sentence or fragment
- code/package names in notes are sometimes formatted in fixed-width/colored text and sometimes in quotes
- language for avoiding all episodes or any other episodes inconsistent (may not be needed in new checkout format)

Additionally, it's worth considering how to indicate explicitly here that choosing a Spanish episode is contingent on checking out with a Spanish-speaking trainer.

Start with the suggested demo episodes page linked in the issue and review its tables, episode lists, notes, punctuation, and Spanish-language guidance. Wait for the revised checkout process to launch before making changes; done means the remaining page styles and wording are consistent with the new format.

Written by the indexing model from the issue text.