This one, for example, doesn't work, because it has a .sh extension.
Another example, this one with a .rb extension.
Here are (all!) the others to test:
Render code snippets as plain-text
With this, we render ".rb", ".html" (etc) snippets.
Note that I may want to eventually allow the HTML snippets to actually
render as HTML, and I also want to syntax-highlight language snippets,
but that can be a task for another day.