Suggestion: Add guides for component css styling to the styleguide

Nobody has claimed this yet.

Was just thinking. In our project at work, we are playing with how to name components and how to use/name the css classes.

We were using [ITCSS](https://css-tricks.com/forums/topic/itcss-an-interesting-way-to-organize-large-scale-projects/) as a base for our css structure Kinda like BEM, SMACSS combined with some extra goodies.
It helps a lot with the lexical scope and stuff.
But when you're building components, your lexical scope is mostly gone and instead of using BEM classes to define your HTML structure you can use your component names (HTML elements) to define structure/make the HTML more readable.

But you're probably still gonna use global styles combined with component styles on your component, therefore it would be nice to see the difference between the two at once.

We thought this could be a nice solution:

Old bem style:

``` html

Start by reviewing the existing styleguide structure and its guidance on component naming and CSS classes. Add a guide that clearly contrasts the shown BEM markup with component-style markup, explains global versus component styles, and documents the proposed double-dash modifier convention.

Written by the indexing model from the issue text.