Register upgrade (#2)

* Update init to take an optional Steam ID. Add register for steam game. Remove url from cmd line params to launched game.

* Start on a build script

examples/button-clicker/Assets/DiscordController.cs

@@ -5,6 +5,7 @@ using UnityEngine;
 public class DiscordController : MonoBehaviour {
     public DiscordRpc.RichPresence presence;
     public string applicationId;
+    public string optionalSteamId;
     public int callbackCalls;
     public int clickCounter;
     public UnityEngine.Events.UnityEvent onConnect;
@@ -72,7 +73,7 @@ public class DiscordController : MonoBehaviour {
         handlers.errorCallback += ErrorCallback;
         handlers.joinCallback += JoinCallback;
         handlers.spectateCallback += SpectateCallback;
-        DiscordRpc.Initialize(applicationId, ref handlers, true);
+        DiscordRpc.Initialize(applicationId, ref handlers, true, optionalSteamId);
     }
 
     void OnDisable()

examples/button-clicker/Assets/DiscordRpc.cs

@@ -47,7 +47,7 @@ public class DiscordRpc
     }
 
     [DllImport("discord-rpc", EntryPoint = "Discord_Initialize")]
-    public static extern void Initialize(string applicationId, ref EventHandlers handlers, bool autoRegister);
+    public static extern void Initialize(string applicationId, ref EventHandlers handlers, bool autoRegister, string optionalSteamId);
 
     [DllImport("discord-rpc", EntryPoint = "Discord_Shutdown")]
     public static extern void Shutdown();

examples/button-clicker/Assets/main.unity

@@ -668,6 +668,7 @@ MonoBehaviour:
     spectateSecret: 
     instance: 0
   applicationId: 345229890980937739
+  optionalSteamId: 
   callbackCalls: 0
   clickCounter: 0
   onConnect: