Feat request: <!-- SOURCE -->

[deini]

Feat request

Followup of: #113

What do you guys think about a <!-- SOURCE --> placeholder that would add the story source to the markdown as a code snippet?

[tuchk4]

released at storybook-readme@5.0.7-alpha.0+5c71e7a

I will update snapshots laters

@deini Would be nice if you have time to add a property to auto-format source code.

And another feature request -- wrap story source with the collpasable box. (just to make it looks different from code blocks) Like this:

Story source

  function whatIsLove() {
    console.log('Baby Don't hurt me. Don't hurt me');
    return 'No more';
  }

What do you think?