package list: support highlighting more languages in Markdown code snippets

[anmonteiro]

and example is https://ocaml.org/p/melange-fest/latest which has ReasonML examples. They are, however, not properly highlighted.

[sabine]

@anmonteiro Is this issue about the README, or also about the documentation?

[sabine]

I think this needs to be done upstream in the hilite library, but this is a good task.