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/_SeeAlso.cshtml

@@ -0,0 +1,14 @@
+@using Statiq.CodeAnalysis
+@{
+    var seeAlso = Document.GetList<string>(CodeAnalysisKeys.SeeAlso);
+    if (seeAlso?.Count > 0)
+    {
+        <h3 id="SeeAlso">See Also</h3>
+        <ul>
+            @foreach (string seeAlsoComment in seeAlso)
+            {
+                <li>@Html.Raw(seeAlsoComment)</li>
+            }
+        </ul>
+    }
+}