Use Chromatic to host our Storybook

Created by: felixfbecker

As we get more designers on the team, we need to make sure design and engineering is a two-way street, so we can discover any inconsistencies.

We have Storybook for our component library. It doesn't include all components yet, but improves developer experience a lot and can also be used for screenshot testing. Components in the storybook can easily be looked at by designers without having to reproduce a lot of backend state.

However, they currently still require cloning and building the repo, which is not a hurdle for engineers, but is one for designers. There is also no channel to discuss what is inside the storybook.

Chromatic by the storybook creators solves this. It can host our storybook and allows commenting on it (more granularly than in Percy). It supports versioning (tied to git) and can replace our use of Percy for Storybook screenshot tests.

cc @AlicjaSuska @rrhyne