Add css so that more known languages are processed

Hi,

in less-docs if a language isn't in this file it gets processed by marked-default using potentiolly a different version of highlight-js.

It looks like this is the main language missing for less-docs. By setting this I get consistent highlighting in less-docs. Not sure if there is an easier way to do it - perhaps fallback to checking if highlight js supports a language rather than mapping everything it supports.