GFM admonition blocks

[bric3]

Is your feature request related to a problem? Please describe.
Github now support admonition blocks

> [!NOTE]  
> Highlights information that users should take into account, even when skimming.

> [!TIP]
> Optional information to help a user be more successful.

> [!IMPORTANT]  
> Crucial information necessary for users to succeed.

> [!WARNING]  
> Critical content demanding immediate user attention due to potential risks.

> [!CAUTION]
> Negative potential consequences of an action.

Note

Highlights information that users should take into account, even when skimming.

Tip

Optional information to help a user be more successful.

Important

Crucial information necessary for users to succeed.

Warning

Critical content demanding immediate user attention due to potential risks.

Caution

Negative potential consequences of an action.

Describe the solution you'd like
Ideally adding a new gfm extension to common-mark makes sense, to support this admonition syntax.

Describe alternatives you've considered
No alternatives.

Additional context
Source [1], [2]