Refactor localization in sidebar action classes

Updated `PinFolderToSidebarAction.cs` and `UnpinFolderToSidebarAction.cs` to retrieve localized strings using a `Strings` class instead of string literals. This change enhances maintainability and organization of localization resources.

Author: mrashutoshnigam

src/Files.App/Actions/Sidebar/PinFolderToSidebarAction.cs

@@ -11,10 +11,10 @@ internal sealed partial class PinFolderToSidebarAction : ObservableObject, IActi
 		private readonly IQuickAccessService service;
 
 		public string Label
-			=> "PinFolderToSidebar".GetLocalizedResource();
+			=> Strings.PinFolderToSidebar.GetLocalizedResource();
 
 		public string Description
-			=> "PinFolderToSidebarDescription".GetLocalizedResource();
+			=> Strings.PinFolderToSidebarDescription.GetLocalizedResource();
 
 		public RichGlyph Glyph
 			=> new(themedIconStyle: "App.ThemedIcons.FavoritePin");

src/Files.App/Actions/Sidebar/UnpinFolderToSidebarAction.cs

@@ -9,10 +9,10 @@ internal sealed partial class UnpinFolderFromSidebarAction : ObservableObject, I
 		private readonly IQuickAccessService service;
 
 		public string Label
-			=> "UnpinFolderFromSidebar".GetLocalizedResource();
+			=> Strings.UnpinFolderFromSidebar.GetLocalizedResource();
 
 		public string Description
-			=> "UnpinFolderFromSidebarDescription".GetLocalizedResource();
+			=> Strings.UnpinFolderFromSidebarDescription.GetLocalizedResource();
 
 		public RichGlyph Glyph
 			=> new(themedIconStyle: "App.ThemedIcons.FavoritePinRemove");