Add support for alerts (#26)

Author: sandydoo

fixture.md

@@ -11,6 +11,16 @@
 
 <img src="image.png" width="182" align="right">
 
+#### Alerts
+
+> [!NOTE]
+> Highlights information that users should take into account, even when skimming.
+
+> [!IMPORTANT]
+> Crucial information necessary for users to succeed.
+
+> [!WARNING]
+> Critical content demanding immediate user attention due to potential risks.
 
 ### Code snippet
 

index.js

@@ -111,6 +111,15 @@ const ALLOW_CLASS = new Set([
 	'.contains-task-list',
 	'.task-list-item',
 	'.task-list-item-checkbox',
+	// For Markdown alerts.
+	'.markdown-alert',
+	'.color-fg-accent',
+	'.color-fg-attention',
+	'.color-fg-done',
+	'.text-semibold',
+	'.d-inline-flex',
+	'.flex-items-center',
+	'.mb-1',
 ]);
 
 function extractStyles(rules, ast) {