[TYPO3] Editing CSS in extension (specifically sr_language_menu)

[Mark Pi]

I'm having problems configuring the CSS for the sr_language_menu extension.

The documentation states: "Configure the default CSS selectors included 
in the extension according to the visual design of your site."

There's no CSS external CSS file (that I can find), and overwriting the 
CSS in my CSS file doesn't work.

There's nothing in the CSS styler.

How is CSS edited in this extension? Surely you don't have to create a 
TS wrap just to change one CSS setting.