Add PowWorker to mine Nostr events off the main thread

src/workers/pow.worker.ts

@@ -0,0 +1,10 @@
+import * as Comlink from 'comlink';
+import { nip13, type UnsignedEvent } from 'nostr-tools';
+
+export const PowWorker = {
+  mine<K extends number>(event: UnsignedEvent<K>, difficulty: number) {
+    return nip13.minePow(event, difficulty);
+  },
+};
+
+Comlink.expose(PowWorker);