This commit updates the theme colors in the Storybook configuration to
use the new global color definitions. The changes include replacing
greyscale colors with their corresponding gray colors for consistency.
Additionally, the theme structure has been refactored to align with the
updated token architecture, enhancing maintainability and ensuring a
cohesive design system across the application.
With the latest version of storybook, our documentation were broken as
we were trying to access to a property from an object that does not
exist anymore. In fact, in the preview context, a property `globals`
has been renamed `userGlobals`.
We want to be able to visualize easily themes directly inside
Storybook. This was not a trivial task as there is no centralized
logic to handle Doc / Stories / Manager at the same time.
