Refactor NavigationTrans and PropertyManager classes

- Removed unused `using System.Diagnostics.CodeAnalysis;` directive.
- Changed `PropertyManager` from a static class to a static file class.
- Fixed initialization of `properties` dictionary to use `new Dictionary<BindableObject, BaseCustomAnimation>()`.
- Updated `Add` method to correctly store values in the `properties` dictionary.
- `Get` method remains unchanged in functionality.

Author: pictos

PJ.NavigationTrans.Maui/NavigationTrans.cs

@@ -1,5 +1,4 @@
-using System.Diagnostics.CodeAnalysis;
-using System.Runtime.CompilerServices;
+using System.Runtime.CompilerServices;
 
 namespace PJ.NavigationTrans.Maui;
 public static class NavigationTrans
@@ -43,12 +42,12 @@ static void RegisterCustomTransitions(BindableObject view)
 
 }
 
-static class PropertyManager
+static file class PropertyManager
 {
 	static readonly Dictionary<BindableObject, BaseCustomAnimation> properties = [];
 
 	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	public static void Add(BindableObject key, BaseCustomAnimation value) => 
+	public static void Add(BindableObject key, BaseCustomAnimation value) =>
 		properties[key] = value;
 
 	[MethodImpl(MethodImplOptions.AggressiveInlining)]