Add timeout to http client requests (#1351)

## Description
`fetch` does not have a default timeout, so there is a non-zero chance
of our HTTP requests to WorkOS servers hanging indefinitely. This PR
introduces `timeout` as an optional parameter while initializing WorkOS
client to terminate the request if its taking longer than `timeout`
milliseconds.

## Documentation

Does this require changes to the WorkOS Docs? E.g. the [API
Reference](https://workos.com/docs/reference) or code snippets need
updates.

```
[ ] Yes
```

If yes, link a related docs PR and add a docs maintainer as a reviewer.
Their approval is required.