refactor: send initial entity state

packages/entity/list/index.js

@@ -204,6 +204,16 @@ export class EntityList extends decorate(class {}) {
     }
   }
 
+  toNetwork(informed) {
+    const {areaToInform} = informed;
+    const visibleEntities = this.visibleEntities(areaToInform);
+    // Mark as notified.
+    this._informedEntities.set(informed, visibleEntities);
+    return visibleEntities.map((entity) => {
+      return entity.mergeDiff();
+    });
+  }
+
   toJSON() {
     const json = [];
     for (let i = 0; i < this._flatEntities.length; i++) {