I was going to try to investigate issue #104, which is also affecting me, but when I tried to build the add-on, I got the following error after downloading highlight.js:
Checking that all CSS styles from highlight.js are listed in the add-on...
[WARNING] Found missing CSS style: "intellij-light".
make: *** [Makefile:40: check_css_list] Error 1`
In a quick look, it seems this is just because highlight.js included some styles that are not listed in the add-on.