Unify manager-plugin namespace to Mummert

src/Compat/Contao/Manager/Plugin.php

@@ -0,0 +1,9 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Mummert\FilteredEventsExportBundle\Contao\Manager;
+
+class Plugin extends \FilteredEventsExportBundle\Contao\Manager\Plugin
+{
+}

src/Compat/FilteredEventsExportBundle.php

@@ -0,0 +1,9 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Mummert\FilteredEventsExportBundle;
+
+class FilteredEventsExportBundle extends \FilteredEventsExportBundle\FilteredEventsExportBundle
+{
+}