Enhance the display of which tag (environment) is effective (dotnet#17013)

Author: guardrex

aspnetcore/fundamentals/environments/sample-snapshot/EnvironmentsSample/Pages/About.cshtml

@@ -1,11 +1,12 @@
 <environment include="Development">
-    <div>&lt;environment include="Development"&gt;</div>
+    <div>The effective tag is: &lt;environment include="Development"&gt;</div>
 </environment>
 <environment exclude="Development">
-    <div>&lt;environment exclude="Development"&gt;</div>
+    <div>The effective tag is: &lt;environment exclude="Development"&gt;</div>
 </environment>
 <environment include="Staging,Development,Staging_2">
     <div>
+        The effective tag is:
         &lt;environment include="Staging,Development,Staging_2"&gt;
     </div>
 </environment>