Using `...` syntax on exposed API.

Hey team, I just had some fun debugging this! I have some code where I essentially do:

```
function blah (...args) {
const api = Comlink.wrap(worker);
return api[name](...args);
}
```

Where the splat function call transpiles to:

```
return api[name].apply(api, args);
```

The `.apply` triggers the `get` trap on the `Proxy` which returns another `Proxy`, and chaos ensues 😅

I guess you could maybe add another guard to the `get` trap for this case? For now I'll just target ES2015!