[eslint-config-kyt] Add eslint-plugin-css-modules

[tizmagik]

Given that CSS Modules is a core opinion of kyt, I think it makes sense to add this eslint-plugin, eslint-plugin-css-modules.

Versions of kyt, node, OS

Current

Bug or Feature?

Feature

Current Behavior

No warnings/errors when there's unused CSS classnames

Desired Behavior

Warnings/errors when there's unused CSS classnames (or using a classname that does not exist, silently resolves to "undefined" currently).