src/Plugin.php
protected function attachListenerOn(Application $app, $event, Closure $callback)
    {
        $app->make('events')->listen("orchestra.{$event}: extension.{$this->extension}", $callback);
    }
protected function attachListenerOn(Application $app, $event, Closure $callback)
    {
        $app->make('events')->listen("orchestra.{$event}: extension.{$this->extension}", $callback);
    }
Attach event listener.

@param  \Illuminate\Contracts\Foundation\Application  $app
@param  string  $event
@param  \Closure  $callback

@return void