Theme Storybook with global dark and light theme

Created by: felixfbecker

Instead of having a toggle in the knobs panel that only toggles the theme for the component, this adds a global toggle in the top bar that toggles dark mode for all components and the Storybook UI itself. It defaults and reacts to the OS theme. Defines a theme for Storybook that matches our webapp styles and replace the Storybook logo and favicon with the logo of our design system.