feat: auto-bound methods

[buschtoens]

Example using the {{pick}} helper from ember-composable-helpers to get the event.target.checked property.

<label>
  Enable dark mode
  <input
    type="checkbox"
    checked={{get (service "theme") "isDark"}}
    {{on "input" (pick "target.checked" (service "theme" "toggleDarkMode"))}}
  >
</label>

export default class ThemeService extends Service {
  @tracked isDark = false;

  toggleDarkMode(newValue = !this.isDark) {
    // Even though this method isn't using `@action`, the `{{service}}` helper
    // binds it to the service instance.
    this.isDark = newValue;
  }
}