Draft: Resolve "Integration of storybook for component library"

Closes #506 (closed)

Simple example of some components within a storybook. Includes:

• Storybooks for a few components as example [1]
• Refactoring of providers, now there is a single Providers components with the providers needed to run the app. This can be used for: (regular) app, tests and storybooks
• Refactoring of page structure for the ContributionEditor, following the 'one component per folder' structure. )Folders can contain tests, storybooks, hooks and of course the component itself.)

Todos:

• Add additional stories for components
• Integrate mock service worker. For some reasons I had trouble doing so, the page kept reloading. Maybe it's a bug in Storybook. If so, another solution would be to fetch all API calls and just return 200
• Deploy to Gitlab pages (add to Gitlab-ci file, should be straightforward)

[1]