[Feature Request] Supporting aside (or admonitions or callouts) in the Markdown

[roberto-butti]

Supporting Aside (or admonitions or callouts) in the markdown.
Asides (also known as “admonitions” or “callouts”) are useful for displaying secondary information alongside a page’s main content.
Provide a custom Markdown syntax for rendering asides. Aside blocks are indicated using a pair of triple colons ::: to wrap your content, and can be of type note, tip, caution or danger.

• Astro Starlight : https://starlight.astro.build/guides/authoring-content/#asides
• Vuepress : https://vuepress.vuejs.org/guide/markdown.html#custom-containers

Example:

:::note
This is a note
:::

[roberto-butti]

I'm starting to work on this PR.
I will follow this great tutorial for creating the markdown extension https://www.honeybadger.io/blog/php-markdown/

[roberto-butti]

Closed by #17