update highlight.js for sparql and turtle

[VladimirAlexiev]

Hi @hakimel! We need highlighting for the semantic web languages sparql and turtle.
highlightjs/highlight.js#1553 adds them to highlight.js, but they are not yet in the release (the PR has been waiting 10 months).

reveal.js includes a local minified version of highlight.js (9.11.0), which is 13 months old.

1. What is the process of upgrading highlight.js?
2. What languages do you include since https://highlightjs.org/download/ allows one to select languages? Or do you include all highlight.js languages

[VladimirAlexiev]

1. https://github.com/VladimirAlexiev/highlight-to-reveal explains such process, and has a simple shell script to upgrade reveal from a highlight build
2. It seems to me that reveal includes highlight's :common languages.

PR #2160 fixes this. It adds languages :common sparql ttl.