Class TimeoutError public

A TimeoutError is used by an adapter to signal that a request to the external API has timed out. I.e. no response was received from the external API within an allowed time period.

An example use case would be to warn the user to check their internet connection if an adapter operation has timed out:

```js {data-filename=app/routes/application.js} import Route from '@ember/routing/route'; import { TimeoutError } from '@ember-data/adapter/error'; import { action } from '@ember/object';

export default class ApplicationRoute extends Route {