Add basic multiplayer

shared/src/objects/game-object.ts

@@ -0,0 +1,12 @@
+import { CommandReceiver } from '../commands/command-receiver';
+import { Id } from '../transport/identity';
+
+export abstract class GameObject extends CommandReceiver {
+  public get type(): string {
+    return (this as any).constructor.type;
+  }
+
+  constructor(public readonly id: Id) {
+    super();
+  }
+}