Update throttle docs

reactiveweb/src/throttle.ts

@@ -4,6 +4,22 @@ import { cell, resource } from 'ember-resources';
  * A utility that creates a resource allowing us to throttle execution of a function.
  * Especially useful for rate limiting execution of handlers on events like resize and scroll.
  *
+ * ```js
+ *  import Component from '@glimmer/component';
+ *  import { tracked } from '@glimmer/tracking';
+ *  import { use } from 'ember-resources';
+ *  import { throttle } from 'reactiveweb/throttle';
+ *
+ *  const delay = 100; // ms
+ *
+ *  class Demo extends Component {
+ *    @tracked _userInput = 'initial';
+ *
+ *    // immediately returns 'initial', and all updates will be throttled
+ *    // to update only after 100ms since the last value was detected.
+ *    @use userInput  = throttle(100, () => this._userInput);
+ * ```
+ *
  * @param delay A zero-or-greater delay in milliseconds. For event callbacks, values around 100 or 250 (or even higher) are most useful.
  * @param callback A function to be executed after delay milliseconds.
  */