Doc: Add instructions to use HTML links inside callouts

[bph]

As a follow up on #50110 that fixed #50109 - the contributor handbook (block editor) needs an update.
Section to update: Documentation Contributions > Callout notices

To add a comment that without the div tags, Markdown links don't work, but

Also the page needs to updated again as the parser didn't do the 'normal' link parsing.

https://developer.wordpress.org/docs/reference-guides/block-api/block-metadata.md
Should have been converted to
https://developer.wordpress.org/block-editor/reference-guides/block-api/block-metadata/

And https://developer.wordpress.org/docs/getting-started/create-block/README.md
Should be https://developer.wordpress.org/block-editor/getting-started/create-block/

I am uncertain if that is expected or a bug in the link parser...

It definitely needs to be fixed on the modified page, though.

Step-by-step reproduction instructions

Got to https://developer.wordpress.org/block-editor/reference-guides/block-api/block-registration/
Follow the links in the yellow call out box.
They all 404.

Screenshots, screen recording, code snippet