Docs redesign (#728)

* Adding a dark mode
* Adding reference for types to summary pages
* Adding API Reference
* Adding modifiers to methods/fields/etc
* Minimizing files input
* Caching a lot of the output pages
* Cache only for each execution
* Adding API references to existing docs

docs/src/Shortcodes/AlertShortcode.cs

@@ -1,6 +1,5 @@
 using System.Collections.Generic;
 using Statiq.Common;
-using System.Xml.Linq;
 
 namespace Docs.Shortcodes
 {
@@ -8,7 +7,6 @@ namespace Docs.Shortcodes
     {
         public override ShortcodeResult Execute(KeyValuePair<string, string>[] args, string content, IDocument document, IExecutionContext context)
         {
-
             return $"<div class=\"alert-warning\">{content}</div>";
         }
     }