feat(scenarios): add buy me a coffee maui library

Create a .NET MAUI library for Buy Me a Coffee integration with branded button, QR code, and widget controls. Includes 8 theme presets (yellow, black, white, blue, violet, orange, red, green), customizable styling, and SkiaSharp-based rendering. Supports opening BMC pages in browser and generating QR codes for donations.

BuyMeCofee.Maui/BuyMeACoffeeExtensions.cs

@@ -0,0 +1,16 @@
+using SkiaSharp.Views.Maui.Controls.Hosting;
+
+namespace BuyMeCofee.Maui;
+
+public static class BuyMeACoffeeExtensions
+{
+    /// <summary>
+    /// Registers Buy Me a Coffee controls and their dependencies (SkiaSharp).
+    /// Call this in your MauiProgram.cs CreateMauiApp() builder.
+    /// </summary>
+    public static MauiAppBuilder UseBuyMeACoffee(this MauiAppBuilder builder)
+    {
+        builder.UseSkiaSharp();
+        return builder;
+    }
+}