Bug: Deployment failed in Vercel following MiniKit Tutorial

### Describe the bug and the steps to reproduce it

1. Follow the steps from https://docs.base.org/builderkits/minikit/quickstart till "Deploying to Vercel" section.
2. Install Vercel CLI.
3. Try deploying the project with the command "vercel".
4. Vercel returns a build error:
```
x 'import', and 'export' cannot be used outside of module code
,-[48:1]
48 | self.addEventListener('beforeunload', () => {
49 | stopHeartbeat();
50 | });
51 | export {};
: ^^^^^^
52 | //# sourceMappingURL=HeartbeatWorker.js.map
`----
Caused by:
0: failed to parse input file
1: Syntax Error
> Build failed because of webpack errors
Error: Command "npm run build" exited with 1
```

### What's the expected behavior?

The miniapp should deploy correctly on Vercel, but the presence of `export {};` prevents it. The error originates from the module `@coinbase/wallet-sdk/dist/sign/walletlink/relay/connection/HeartbeatWorker.js`. I resolved the issue by simply removing the `export {};` statement, which allowed the build to succeed locally—previously, it failed both locally and on Vercel.


### What version of the libraries are you using?

- OnChainKit: 0.38.13