Ah ok, the CSS you posted does not work anymore.
I think best way to accomplish this would be to add a plugin outlet to the category-title-link template, and use a widget to add the appropriate icon before the category name. It makes sense to me for the Category Icons component to optionally include the category icon in the categories list. If you only want icons to display on the category list, you could hide them from the other locations with CSS.
@pmusaraj what do you think? If you think it’s a good idea, I can make a PR for the plugin outlet, then try to work out a PR for the Category Icons component that will add this functionality.