Move PackageProjectUrlAttribute to new Attributes folder

PR comment

Author: michael-hawker

common/CommunityToolkit.Labs.Shared/Helpers/PackageProjectUrlAttribute.cs renamed to common/CommunityToolkit.Labs.Shared/Attributes/PackageProjectUrlAttribute.cs

@@ -21,14 +21,14 @@
     <Compile Include="$(MSBuildThisFileDirectory)AppLoadingView.xaml.cs">
       <DependentUpon>AppLoadingView.xaml</DependentUpon>
     </Compile>
+    <Compile Include="$(MSBuildThisFileDirectory)Attributes\PackageProjectUrlAttribute.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Behaviors\NavigateToUriAction.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Controls\TitleBar\TitleBar.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Converters\SubcategoryToIconConverter.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)DocOrSampleTemplateSelector.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Helpers\BackgroundHelper.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Helpers\IconHelper.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Helpers\NavigationViewHelper.cs" />
-    <Compile Include="$(MSBuildThisFileDirectory)Helpers\PackageProjectUrlAttribute.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Pages\GettingStartedPage.xaml.cs">
       <DependentUpon>GettingStartedPage.xaml</DependentUpon>
     </Compile>