RFC: New testing concept

[gfellerph]

Requirements:

• Packages can be individually tested. At the moment, some tests depend on the documentation to run
• Tests run faster
• Tests run in parallel
• Visual regression tests test only one component in one state
• Visual regression tests run on every PR
• Coverage reports
• It's easy to run tests with commands like pnpm --filter ...design-system-components... test (tests all up- and downstream dependencies as well as the components)

POC new technologies:

• Storybook chromatic
• Playwright