message: docs: update callback and onLoaded docs
diff: @@ -167,6 +167,19 @@ Also you can pass options:
  Here are detailed [options docs](#redoc-options-object).
  +You can also specify `onLoaded` callback which will be called each time Redoc has been fully rendered or when error occurs (with an error as the first argument). *NOTE*: It may be called multiply times if you change component properties
  +
  +```js
  +<RedocStandalone
  + specUrl="http://rebilly.github.io/RebillyAPI/swagger.json"
  + onLoaded={error => {
  + if (!error) {
  + console.log('Yay!');
  + }
  + }}
  +/>
  +```
  +
  ## ReDoc CLI
  [See here](https://github.com/Rebilly/ReDoc/blob/master/cli/README.md)
  @@ -218,7 +231,7 @@ Redoc.init(specOrSpecUrl, options, element, callback?)
  - `specOrSpecUrl` is either JSON object with specification or an URL to the spec in `JSON` or `YAML` format
  - `options` [options object](#redoc-options-object)
  - `element` DOM element to put ReDoc into
  -- `callback` (optional) - callback to be called after Redoc has been fully rendered
  +- `callback` (optional) - callback to be called after Redoc has been fully rendered. It is also called also on errors with error as the first argument
  ```js
  Redoc.init('http://petstore.swagger.io/v2/swagger.json', {
  