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/input/api/Sections/_Examples.cshtml

@@ -0,0 +1,9 @@
+@using Statiq.CodeAnalysis
+@{
+    var examples = Document.GetString(CodeAnalysisKeys.Example);
+    if (!examples.IsNullOrWhiteSpace())
+    {
+        <h3>Examples</h3>
+        <div>@Html.Raw(examples)</div>
+    }
+}