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

examples/Cli/Demo/Commands/Add/AddSettings.cs

@@ -1,7 +1,7 @@
 using System.ComponentModel;
 using Spectre.Console.Cli;
 
-namespace Demo.Commands;
+namespace Demo.Commands.Add;
 
 public abstract class AddSettings : CommandSettings
 {