React-pdf: Request: Don't enforce the use of a CSS loader

Might be related to #133. It seems with the newer versions of react-pdf, you get this error when you don't have a CSS loader:

ERROR in ./node_modules/react-pdf/build/annotation_layer_builder.css
Module parse failed: Unexpected token (16:0)
You may need an appropriate loader to handle this file type.
|  */
| 
| .annotationLayer section {
|   position: absolute;
| }
 @ ./node_modules/react-pdf/build/PageAnnotations.js 35:0-41
 @ ./node_modules/react-pdf/build/Page.js
 @ ./node_modules/react-pdf/build/entry.noworker.js
 @ ./src/features/preview/components/Preview.js
 @ ./src/features/preview/components/index.js
 @ ./src/app/pages/Generator.js
 @ ./src/app/App.js
 @ ./src/index.js
 @ multi (webpack)-dev-server/client?http://localhost:3000 webpack/hot/dev-server babel-polyfill ./index.js

This is a bit inconvenient for a couple reasons:

1. Annotations aren't rendered because I have renderAnnotations={false}, which makes it a bit strange that its still trying to use this CSS
2. People who use css in js solutions like styled-components don't really need to use CSS loaders, so it's a bit annoying to have to include it just for this package.

Just my thoughts on this, feel free to close this out if its too similar to #133 or if you don't want to remove this behavior.