Support markdown short link

[unional]

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

Currently, the Markdown component from @storybook/blocks does not understand short link:

// src/overview.mdx
import { Markdown } from '@storybook/blocks'
import readme from '../readme.md?raw'

<Markdown>{readme}</Markdown>

// readme.md
[link A](http:...) // works
[link B][link-b] // works
[link-c] // doesn't work, renders `[link-c]`.

[link-b]: http:...
[link-c]: http:...

Describe the solution you'd like

Support the [link-c] context.

Describe alternatives you've considered

No response

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

yes, I can

Additional context

No response