Add to the library the flagAnnotation method. Not available yet in [API docs](https://h.readthedocs.io/en/latest/api-reference/#tag/annotations). Endpoint: https://hypothes.is/api/annotations/:id/flag HTTP Method: PUT Spec.: flagAnnotation(id, callback)
Add to the library the flagAnnotation method. Not available yet in API docs.
Endpoint: https://hypothes.is/api/annotations/:id/flag
HTTP Method: PUT
Spec.: flagAnnotation(id, callback)