Consider changing to highlight.js for parsons formatting

[bnmnetp]

prettify.js does not work for several examples, especially Java code like List<String> See #1191 I have no idea where prettify.js comes from as what we have is minified and has no comments. If it is a branch of google's code-prettify then we should definitely move on as the project is archived.

It seems that https://highlightjs.org is a good alternative.