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/canvas.md

@@ -1,6 +1,7 @@
 Title: Canvas
 Order: 60
 Description: "**Canvas** is a widget that allows you to render arbitrary pixels to the console."
+Reference: T:Spectre.Console.Canvas
 ---
 
 `Canvas` is a widget that allows you to render arbitrary "pixels"