Delaire: I'm not aware of an existing LaTeX plugin or add on.
Addon creation is done through the SDK.
Although, I'm not sure how you would make such a software, knowing the current text sources in C2 are the text, textbox and spritefont objects.
Study those already and see if you think you could format their text thanks to a third-part plugin or behavior. Some of them already support CSS.
Snikoggs: In another sticky topic named : How to install plugins and behaviors.
If you have issues with a specific addon, consider posting in the topic of this addon to get support from its author.
As it is a behavior, you should only see it appear in the Add behavior dialog, nowhere else.