Added docs to CupertinoAlertDialog to explain title, content, and button styling (#18128) (#18129)

packages/flutter/lib/src/cupertino/dialog.dart

@@ -106,9 +106,17 @@ class CupertinoDialog extends StatelessWidget {
 /// An iOS-style alert dialog.
 ///
 /// An alert dialog informs the user about situations that require
-/// acknowledgement. An alert dialog has an optional title and an optional list
-/// of actions. The title is displayed above the content and the actions are
-/// displayed below the content.
+/// acknowledgement. An alert dialog has an optional title, optional content,
+/// and an optional list of actions. The title is displayed above the content
+/// and the actions are displayed below the content.
+///
+/// This dialog styles its title and content (typically a message) to match the
+/// standard iOS title and message dialog text style. These default styles can
+/// be overridden by explicitly defining [TextStyle]s for [Text] widgets that
+/// are part of the title or content.
+///
+/// To display action buttons that look like standard iOS dialog buttons,
+/// provide [CupertinoDialogAction]s for the [actions] given to this dialog.
 ///
 /// Typically passed as the child widget to [showDialog], which displays the
 /// dialog.
@@ -116,6 +124,7 @@ class CupertinoDialog extends StatelessWidget {
 /// See also:
 ///
 ///  * [CupertinoDialog], which is a generic iOS-style dialog.
+///  * [CupertinoDialogAction], which is an iOS-style dialog button.
 ///  * <https://developer.apple.com/ios/human-interface-guidelines/views/alerts/>
 class CupertinoAlertDialog extends StatelessWidget {
   /// Creates an iOS-style alert dialog.