Unify color theme for all kind of code snippets

[imagoiq]

Is your feature request related to a problem? Please describe.

As a Storybook maintainer, I would like to choose a color theme (light or dark) for all the code snippets displayed in storybook. That includes:

• "Markdown style" fenced code blocks (e.g. ```html …. ```) in MDX
• Markdown converted to MDX with the Markdown blocks
• Source of stories

Related issue:

Since Storybook 7, we cannot anymore add a dark parameter to Markdown style fenced code blocks in MDX: #21626

Describe the solution you'd like

Set a default dark config in the preview file like

const preview: Preview = {
    …
    parameters: {
      docs: {
        dark: true,
      }
    }
   …
}

Describe alternatives you've considered

No response

Are you able to assist to bring the feature to reality?

no

Additional context

No response