Migrate SkiaSharp documentation from Xamarin.Forms to .NET MAUI

[Copilot]

This PR comprehensively migrates all SkiaSharp documentation from Xamarin.Forms to .NET MAUI, addressing the fact that Xamarin.Forms was replaced by .NET MAUI and the documentation needed to be updated for current developers.

Changes Made

Namespace and Package Updates

• Updated all references from SkiaSharp.Views.Forms to SkiaSharp.Views.Maui.Controls
• Changed Xamarin.Forms namespace references to Microsoft.Maui.Controls
• Updated XAML namespace declarations from http://xamarin.com/schemas/2014/forms to http://schemas.microsoft.com/dotnet/2021/maui
• Migrated package installation instructions from SkiaSharp.Views.Forms to SkiaSharp.Views.Maui.Controls

Documentation Metadata

• Updated ms.service from xamarin to dotnet-maui
• Changed ms.subservice from xamarin-skiasharp to skiasharp
• Updated no-loc directives from [Xamarin.Forms, Xamarin.Essentials] to [.NET MAUI, Microsoft.Maui]

Content Updates

• Migrated all text references from "Xamarin.Forms applications" to ".NET MAUI applications"
• Updated platform requirements (iOS 8.0+ → iOS 11.0+)
• Revised integration examples with correct .NET MAUI XAML syntax
• Updated API references including color classes (Xamarin.Forms.Color → Microsoft.Maui.Graphics.Color)
• Modified cross-reference links to point to Microsoft.Maui documentation

Code Examples

Updated XAML examples throughout the documentation:

<!-- Before -->
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:skia="clr-namespace:SkiaSharp.Views.Forms;assembly=SkiaSharp.Views.Forms">

<!-- After -->
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:skia="clr-namespace:SkiaSharp.Views.Maui.Controls;assembly=SkiaSharp.Views.Maui.Controls">

Files Affected

• 80+ documentation files across all categories (basics, bitmaps, curves, transforms, paths, effects)
• Main overview page (docs/index.md)
• Integration guide (docs/docs/basics/integration.md)
• All section index and tutorial pages

Impact

This migration ensures that developers using .NET MAUI will have accurate, up-to-date documentation for integrating SkiaSharp into their applications. All examples, API references, and setup instructions now correctly reflect the current Microsoft technology stack, making the documentation relevant for modern .NET MAUI development.

The changes maintain complete technical accuracy while providing a seamless experience for developers transitioning from Xamarin.Forms or starting fresh with .NET MAUI.

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