Add example of mixing {x:Bind} and {Binding} in reusable Styles

[Copilot]

This PR addresses a documentation gap by adding a comprehensive example showing how to use both {x:Bind} and {Binding} markup extensions within a reusable Style defined in a Resource Dictionary.

Changes Made

New Section Added: "Mixing {x:Bind} and {Binding} in a reusable Style"

The example demonstrates:

• A complete ResourceDictionary with code-behind that defines properties for {x:Bind}
• A Button style that combines both binding types strategically:
  • {Binding} for DataContext-dependent properties (background, foreground, hover colors)
  • {x:Bind} for compile-time known properties (indicator, pressed state)
• A ViewModel implementing INotifyPropertyChanged for runtime theming
• Usage examples showing how to apply the style in both UWP and Windows App SDK contexts

Technical Benefits

The example shows developers how to:

• Leverage the performance benefits of {x:Bind} for static/compile-time properties
• Use the flexibility of {Binding} for dynamic/runtime scenarios
• Create truly reusable styles that support both approaches
• Implement runtime theming while maintaining optimal performance

Files Modified

• uwp/data-binding/data-binding-in-depth.md - Added example for UWP applications
• hub/apps/develop/data-binding/data-binding-in-depth.md - Added example for Windows App SDK applications

The documentation now provides the missing guidance requested by developers who want to understand how to effectively combine both binding approaches in reusable XAML resources.

Fixes #4609.

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✅ Validation status: passed

File	Status	Preview URL	Details
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uwp/data-binding/data-binding-in-depth.md	✅Succeeded

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Learn Build status updates of commit 828fc06:

✅ Validation status: passed

File	Status	Preview URL	Details
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uwp/data-binding/data-binding-in-depth.md	✅Succeeded

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