doc: Update README and LICENSE.

Author: freezy

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2020 freezy
+Copyright (c) 2021 freezy
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -1,2 +1,49 @@
 # Visual Pinball Engine - PinMAME Gamelogic Engine
 *Enables PinMAME to drive VPE*
+
+[![UPM Package](https://img.shields.io/npm/v/org.visualpinball.engine.pinmame?label=org.visualpinball.engine.pinmame&registry_uri=https://registry.visualpinball.org&color=%2333cf57&logo=unity&style=flat)](https://registry.visualpinball.org/-/web/detail/org.visualpinball.engine.pinmame)
+
+## Structure
+
+This project contains two root folders:
+
+- `VisualPinball.Engine.PinMAME` wraps the [`pinmame-dotnet`](https://github.com/vpinball/pinmame-dotnet)
+library and extends it with some meta data.
+- `VisualPinball.Engine.PinMAME.Unity` is the Unity UPM package that plugs into
+  VPE and implements the gamelogic engine.
+
+### Unity Package
+
+The goal of this repo is to use it within Unity. In order to do that, open the
+Package Manager in Unity, and add `org.visualpinball.engine.missionpinball` under
+*Add package from git URL*.
+
+The Unity package is build and published to our registry on every merge to master.
+
+## Development Setup
+
+In order to import the package locally instead from our registry, clone and
+compile it. This will copy the necessary binaries into the Unity folder. Only
+then, import the project into Unity.
+
+Since the Unity folder contains `.meta` files of the binaries, but not the
+actual binaries, `.meta` files of uncompiled platforms are cleaned up by Unity.
+In order to not accidentally commit those files, we recommend to ignore them:
+
+```bash
+git update-index --assume-unchanged VisualPinball.Engine.PinMAME.Unity/Plugins/linux-x64/PinMame.dll.meta
+git update-index --assume-unchanged VisualPinball.Engine.PinMAME.Unity/Plugins/linux-x64/VisualPinball.Engine.PinMAME.dll.meta
+git update-index --assume-unchanged VisualPinball.Engine.PinMAME.Unity/Plugins/linux-x64/libpinmame.so.3.4.meta
+git update-index --assume-unchanged VisualPinball.Engine.PinMAME.Unity/Plugins/osx-x64/PinMame.dll.meta
+git update-index --assume-unchanged VisualPinball.Engine.PinMAME.Unity/Plugins/osx-x64/VisualPinball.Engine.PinMAME.dll.meta
+git update-index --assume-unchanged VisualPinball.Engine.PinMAME.Unity/Plugins/osx-x64/libpinmame.3.4.dylib.meta
+git update-index --assume-unchanged VisualPinball.Engine.PinMAME.Unity/Plugins/win-x86/PinMame.dll.meta
+git update-index --assume-unchanged VisualPinball.Engine.PinMAME.Unity/Plugins/win-x86/VisualPinball.Engine.PinMAME.dll.meta
+git update-index --assume-unchanged VisualPinball.Engine.PinMAME.Unity/Plugins/win-x86/libpinmame-3.4.dll.meta
+```
+
+## License
+
+This plugin is licensed under the [MIT license](LICENSE). However 
+since we link against PinMAME, the [MAME/BSD-3-Clause](https://github.com/vpinball/pinmame/blob/master/LICENSE)
+must be honored as well.