add new feature to donwload a calendar

Plugin.php

@@ -17,7 +17,8 @@ class Plugin extends PluginBase {
     public function registerComponents() {
         return [
             'NicoSt\GCalendar\Components\Upcoming' => 'upcoming',
-            'NicoSt\GCalendar\Components\EmbeddedCalendar' => 'embeddedCalendar'
+            'NicoSt\GCalendar\Components\EmbeddedCalendar' => 'embeddedCalendar',
+            'NicoSt\GCalendar\Components\Download' => 'download'
         ];
     }