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/Kind/_Assembly.cshtml

@@ -0,0 +1,19 @@
+@using Statiq.CodeAnalysis
+@using Docs.Pipelines
+@using Docs.Extensions
+@foreach (IGrouping<string, IDocument> typeGroup
+    in Outputs.FromPipeline(nameof(Api))
+        .Where(x => x.GetBool(CodeAnalysisKeys.IsResult)
+                    && x.GetString(CodeAnalysisKeys.Kind) == "NamedType"
+                    && Document.IdEquals(x.GetDocument(CodeAnalysisKeys.ContainingAssembly)))
+        .GroupBy(x => x.GetString(CodeAnalysisKeys.SpecificKind))
+        .OrderBy(x => x.Key))
+{
+    <h2>@typeGroup.Key</h2>
+    @foreach (var type in typeGroup)
+    {
+        <ul>
+            <li>@Context.GetTypeLink(type)</li>
+        </ul>
+    }
+}