[Markdown] Support Alerts

[Bizarrus]

In GitHub's Markdown, you can add some alerts:

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

Original:

Package-Site:

Example:

https://code.dlang.org/packages/coldbite?tab=info