Fix comment: default timeout from 30000ms to 60000ms

index.js

  *                   activity takes place )
  *                   If it doesn't exist, the file is downloaded as usual
  *         @property {number} timeout
- *                   Request timeout in millionseconds, by default it's 30000ms.
+ *                   Request timeout in millionseconds, by default it's 60000ms.
  *
  * @return {function} This method returns a `fetch` method instance.
  */