[Feature Request]: Emit download progress to frontend

[fu050409]

What problem does this feature solve?

We don't know how many we downloaded now, neither the status or the download progress. The backend should emit events.

What does the proposed API look like?

app.emit("download.fulfilled", { ...payload });
app.emit("download.failed", { ...payload });

The payload is a serializable and deserializable struct and this should also declare in src/types/payload.ts.