Introduce OnTopic.Attributes as a global using directive

Previously, `OnTopic.Attributes` couldn't be (easily) introduced as a global using directive (e37de82, 1e83841; #53, OnTopicCMS/OnTopic-Library#93) because of a naming conflict with `AttributeDictionary`, which existed in both `OnTopic.Attributes` and `Microsoft.AspNetCore.Mvc.ViewFeatures`. With `AttributeDictionary` renamed to `AttributeValueDictionary` (OnTopicCMS/OnTopic-Library#107), this can be reintroduced.

Author: JeremyCaney

OnTopic.Editor.AspNetCore/Properties/AssemblyInfo.cs

@@ -8,6 +8,7 @@
 | USING DIRECTIVES (GLOBAL)
 \-----------------------------------------------------------------------------------------------------------------------------*/
 global using System.Collections.ObjectModel;
+global using OnTopic.Attributes;
 global using OnTopic.Editor.AspNetCore.Models;
 global using OnTopic.Editor.AspNetCore.Models.Metadata;
 global using OnTopic.Internal.Diagnostics;