feat: move calculation intensive part into a web worker

packages/frontend/src/lib/worker/worker.ts

@@ -0,0 +1,19 @@
+import type { WorkerConract } from '$lib/worker'
+import { packContent, unpackContent } from '@cryptgeon/shared'
+import { expose, transfer } from 'comlink'
+
+const contract: WorkerConract = {
+	pack(input, password) {
+		const content = packContent(input, password)
+		return transfer(content, [content.data.buffer, content.extra.buffer, content.key.buffer])
+	},
+	unpack(data, key) {
+		const content = unpackContent(data, key)
+		return transfer(
+			content,
+			typeof content.data === 'string' ? [] : content.data.map((f) => f.data.buffer)
+		)
+	},
+}
+
+expose(contract)