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/blog/_nextprevious.cshtml

@@ -1,6 +1,4 @@
-
 @inherits StatiqRazorPage<IDocument>
-@model IDocument
 
 @{
     var older = Model.GetDocument(Keys.Next);