How do I access the License API thru here?

Hello, according to Github API docs, you need to attach `application/vnd.github.drax-preview+json` in the `Accept` header. Once that is supplied, one should get the license info along with the repo object. However, I tried the following:

```
const gh = new Github({
username: 'xxxx',
password: 'xxxxxx'
}, '', 'application/vnd.github.drax-preview+json').search()
```

but to no avail. How can I access the License API using this package? Thanks in advance