save config as typescript does not work

will give the error below. It needs to be json.

```
➜  frontend git:(main) ✗ fleek sites deploy
WARN! Fleek CLI is in beta, use it at your own discretion
Error: Validation of loaded /Users/hungcheng/web3/ethereum-boilerplate/frontend/fleek.config.ts failed. File must export config, function that returns config or promise that resolves to config as default export or module export.
```