* Storybook: Add vision statement to intro page

Added the vision statement compiled by the Grafana Labs design system knights to the grafana-ui intro section. Feedback and further improvement ideas welcome!

* Review feedback part 1

_fixed headline formatting
_removed numbered list
_removed paragraph "A library of unified components and styles"
_renamed all occurrences to @grafana/ui
_replaced "ideate" with "determine together"