Include CSS and images in JS file

[camdendotlol]

Summary

• updates the Webpack config for the React app to include styles and images within the editioncrafter.min.js file, rather than as separate files
  • Webpack moves the CSS inline for each element, but preserves the class names. This allows downstream users to modify EC's styling while EC's styling will not affect anything on the page outside of it.
• updates the Storybook config to pull in a live version of the sass files. Previously, you had to run npm run build:css to see CSS changes in Storybook
• removes the CSS-specific build steps and removes anything related to webpack-dev-server

Closes #17

Notes

I'm a little nervous about this one - while I tested it locally by importing the JS bundle into a fresh create-react-app React app, I can't perfectly replicate the conditions of pulling the React package from NPM or pulling the UMD bundle from Unpkg.

[NickLaiacona]

Shall I just accept this and you can push it out to NPM, then we can try it out on editioncrafter-project via unpkg?

[camdendotlol]

@NickLaiacona Sounds good. I also want to merge #39 before creating a new release.