use deletedIds map to sync deletions (#936)

* use deletedIds map for sync deletions

* refactor how we create data for syncing

* fix comments

* streamline broadcast API

* split broadcast methods

src/data/restore.ts

@@ -52,7 +52,7 @@ export function restore(
 
       return {
         ...element,
-        version: element.id ? element.version + 1 : element.version || 0,
+        version: element.version || 0,
         id: element.id || nanoid(),
         fillStyle: element.fillStyle || "hachure",
         strokeWidth: element.strokeWidth || 1,