doc: Update README.

Author: freezy

README.md

@@ -1,12 +1,15 @@
-# HDRP for Visual Pinball Engine
+# Visual Pinball Engine - HDRP Package
 
 *High Definition Render Pipeline support for the Visual Pinball Engine.*
 
-## Where Are We?
+This repository is an [UPM package](https://docs.unity3d.com/Manual/CustomPackages.html) for Unity's [HDRP](https://docs.unity3d.com/Packages/[email protected]/manual/index.html).
 
-![image](https://user-images.githubusercontent.com/70426/102674479-73491000-4196-11eb-8f7f-68b5d21cdf7e.png)
+## Dependency Graph
+
+This package has dependencies to both the [main project](https://github.com/freezy/VisualPinball.Engine) and the [asset library](https://github.com/VisualPinball/VisualPinball.Unity.AssetLibrary).
+
+![image](https://user-images.githubusercontent.com/70426/103706494-25614400-4fad-11eb-9115-fdf1d65b6f11.png)
 
 ## License
 
 [GPL-3.0](LICENSE)
-