Render the "alert" markdown extension

[brianquinlan]

> [!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.

See https://github.com/orgs/community/discussions/16925

[shikharish]

Hello, I would like to work on this issue.

[srawlins]

We would probably accept a PR implementing this, even though it is not specified in https://github.github.com/gfm/ 😠 😡 😠

You can use Markdown text boxes, like this comment box, as a testbed for what GitHub renders. I think we just want to render the right div and p elements, with specific CSS classes. The end clients will then be responsible for making those CSS classes available.

And rigorous testing 😄

[shikharish]

Thank you for the response!
I am new here; excited to contribute to the dart ecosystem!
I could not find a contributing guide to this repo(have never contributed to a dart package before). If you could help me with setting up a development environment that would be really helpful.