Introduced the ReflexiveAttribute view

The `ReflexiveAttribute` view is pretty straight forward: It simply invokes the attribute type view component associated with the `CurrentTopic` (which we assume to be an `AttributeDescriptor`) If the `CurrentTopic` is _not_ an `AttributeDescriptor`, or it is the `ReflexiveAttribute` itself, a warning is displayed. Otherwise, the `CurrentTopic` is rendered as a view component, thus reflecting itself, and fulfilling the requirements of #44.

Author: JeremyCaney

OnTopic.Editor.AspNetCore.Attributes/Views/Editor/Components/Reflexive/Default.cshtml

@@ -0,0 +1,22 @@
+@model AttributeViewModel<AttributeDescriptorViewModel>
+
+@{
+  var isReflexive = Model.CurrentTopic.ContentType == "ReflexiveAttributeDescriptor" || !Model.CurrentTopic.ContentType.EndsWith("AttributeDescriptor");
+  if (isReflexive) {
+    Layout = "~/Areas/Editor/Views/Editor/Components/_Layout.cshtml";
+  }
+}
+
+@if (!isReflexive) {
+  <text>
+    @await Component.InvokeAsync(
+      Model.CurrentTopic.ContentType.Replace("AttributeDescriptor", ""),
+      new { CurrentTopic = Model.CurrentTopic, Attribute = Model.AttributeDescriptor, HtmlFieldPrefix = Html.ViewData.TemplateInfo.HtmlFieldPrefix }
+    )
+  </text>
+}
+else {
+  <div class="alert alert-warning" role="alert">
+    <strong>Note:</strong> This attribute cannot be displayed on topics implementing the @Model.CurrentTopic.ContentType content type.
+  </div>
+}