Feature: Support Github Flavor notes

[n-crespo]

In Github flavored markdown, a note or "alert" can be created with the following syntax:

    > [!Note]
    > *insert note here*

and the note will appear with an icon like so:

[!Note] this is a note

Here is an screenshot:

[!Important] and [!Warning] have a similar layout.

This is not supported in markdown preview, and I would love to see it implemented. I understand, however, if the goal of the plugin is to support vanilla markdown, not the GitHub flavor.

[kiran94]

Linking the official documentation which has the full list of available options https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax#alerts

[kunring]

This would require a plugin for markdown-it. I'm unable to find one on npm.