Convert sync worker to a module, and to typescript

src/platform/web/sync/SyncProxy.ts

@@ -27,7 +27,9 @@ export class SyncProxy implements ISync {
     }
 
     async start(): Promise<void> {
-        this._worker = new SharedWorker(new URL("./sync-worker", import.meta.url));
+        this._worker = new SharedWorker(new URL("./sync-worker", import.meta.url), {
+            type: "module",
+        });
         this._worker.port.onmessage = (event: MessageEvent) => {
             // TODO
             console.log(event);

src/platform/web/sync/sync-worker.ts

@@ -0,0 +1,12 @@
+/// <reference lib="webworker" />
+
+// The empty export makes this a module. It can be removed once there's at least one import.
+export {}
+
+declare let self: SharedWorkerGlobalScope;
+
+self.onconnect = (event: MessageEvent) => {
+    const port = event.ports[0];
+    port.postMessage("hello from sync worker");
+    console.log("hello from sync worker");
+}