Instead of hardcoding the set of supported programming languages and their
aliases in the common.highlightjs module, read those data from a JSON file
instead.
That JSON file is generated during frontend assets processing by webpack
by using the highlightjs library API.
This ensures languages data will always be in sync with current release
of the highlightjs library.
The produced JSON file is stored in git as it is needed to execute backend tests.
Its content might change each time a new release of highlightjs is available.