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/Extensions/StringExtensions.cs

@@ -1,4 +1,4 @@
-namespace Docs
+namespace Docs.Extensions
 {
     public static class StringExtensions
     {