[Storybook] fix(.storybook/preview): sync theme from global with storage key

[TylerAPfledderer]

Description

Fixes issue in Storybook where the update of color mode in the global context was not being recognized in the next-themes provider, as the storage key the provider uses was not updating.

Creates a custom withNextthemes decorator that initializes the global theme and sends it to next-themes via setTheme(). This should ensure the default theme gets to the provider on first load.

See Writing a [next-themes] custom decorator

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[TylerAPfledderer]

@pettinarip hit a blocker with Chromatic check. Not sure if I can do anything about it

[pettinarip]

@pettinarip hit a blocker with Chromatic check. Not sure if I can do anything about it

A re-run did it. A dep fetch had failed.

[pettinarip]

LGTM, thanks @TylerAPfledderer