Improve documentation for `ColorSheme.fromImageProvider` (#129952)

Sample code is added, documentation condensed, and links to guidelines updated.

For b/258360306

packages/flutter/lib/src/material/color_scheme.dart

@@ -898,29 +898,37 @@ class ColorScheme with Diagnosticable {
   /// Generate a [ColorScheme] derived from the given `imageProvider`.
   ///
   /// Material Color Utilities extracts the dominant color from the
-  /// supplied [ImageProvider]. Using this color, a set of tonal palettes are
-  /// constructed. These tonal palettes are based on the Material 3 Color
-  /// system and provide all the needed colors for a [ColorScheme]. These
-  /// colors are designed to work well together and meet contrast
-  /// requirements for accessibility.
+  /// supplied [ImageProvider]. Using this color, a [ColorScheme] is generated
+  /// with harmnonious colors that meet contrast requirements for accessibility.
   ///
   /// If any of the optional color parameters are non-null, they will be
   /// used in place of the generated colors for that field in the resulting
-  /// color scheme. This allows apps to override specific colors for their
+  /// [ColorScheme]. This allows apps to override specific colors for their
   /// needs.
   ///
   /// Given the nature of the algorithm, the most dominant color of the
-  /// `imageProvider` may not wind up as one of the ColorScheme colors.
+  /// `imageProvider` may not wind up as one of the [ColorScheme] colors.
   ///
   /// The provided image will be scaled down to a maximum size of 112x112 pixels
   /// during color extraction.
   ///
+  /// {@tool dartpad}
+  /// This sample shows how to use [ColorScheme.fromImageProvider] to create
+  /// content-based dynamic color schemes.
+  ///
+  /// ** See code in examples/api/lib/material/color_scheme/dynamic_content_color.0.dart **
+  /// {@end-tool}
+  ///
   /// See also:
   ///
+  ///  * [M3 Guidelines: Dynamic color from content](https://m3.material.io/styles/color/dynamic-color/user-generated-color#8af550b9-a19e-4e9f-bb0a-7f611fed5d0f)
+  ///  * <https://pub.dev/packages/dynamic_color>, a package to create
+  ///    [ColorScheme]s based on a platform's implementation of dynamic color.
   ///  * <https://m3.material.io/styles/color/the-color-system/color-roles>, the
   ///    Material 3 Color system specification.
   ///  * <https://pub.dev/packages/material_color_utilities>, the package
-  ///    used to generate the base color and tonal palettes needed for the scheme.
+  ///    used to algorightmically determine the dominant color and to generate
+  ///    the [ColorScheme].
   static Future<ColorScheme> fromImageProvider({
     required ImageProvider provider,
     Brightness brightness = Brightness.light,