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/widgets/barchart.md

@@ -5,6 +5,8 @@ Highlights:
     - Custom colors
     - Labels
     - Use your own data with a converter.
+Reference: T:Spectre.Console.BarChart
+    
 ---
 
 Use `BarChart` to render bar charts to the console.