Easily add syntax highlighting for a language

[njx]

A lot of people have been asking how to configure syntax highlighting for a language, now that we can't edit language.json easily. We should post a simple sample extension. (Or, if it's easy, just add a quick and dirty pref for it...but that might be a little too much to just throw in without some thought.)

[redmunds]

To @dangoor to see how difficult it is to make this a pref.

[dangoor]

FBNC @njx documented on the how to use page

[njx]

Cool. Closing.