Rework Welcome-page, include clear context on what's on display

[julrich]

Currently you could read the welcome page as introducing "just" our very own Design System for various kickstartDS pages. Which is true, but not ultimately the point.

We need to communicate the fact that our Storybook is just one instance demonstrating what's possible for you, as a reader / viewer / potential customer, interested in the framework kickstartDS. It should spark creativity (in comparison to the unstyled core components delivered by the core framework), and make him / her project himself on this backdrop.