message: Update README.md with guidance for .option() usage
diff: @@ -247,6 +247,14 @@ You can pass in additional request headers, either individually or in a dictiona
  ````
  +## .option() and .options()
  +You can pass in additional request options, either individually or in a dictionay. Options can be [node specific](https://github.com/bitinn/node-fetch#options) or [from fetch standard](https://fetch.spec.whatwg.org/#requestinit)
  +```js
  +.option("someOptionName", "someOptionValue")
  +// or
  +.options({"someOptionName":"someOptionValue"})
  +```
  +
  ### .responseType()
  To set a custom response type, use the `.responseType(<ResponseType>)` method. Refer [ResponseType.ts](./src/ResponseType.ts) for available options.
  ````js
  