Find a solution to storybooks importing conflicting styles

[felixfbecker]

Storybooks are for browser, webapp and shared. Webapp components depend on global styles and Bootstrap, but those should not be imported for shared components.

Related issue: storybookjs/storybook#729

Solution proposal:
Use webpack loader to import the styles a component depends on as a string, then render them in a <style> tag in the story-specific decorator.

Noticed by @attfarhan in #9628

This is crucial to solve if we want Percy screenshot tests for Storybooks (#9565).