render max_imagesize in header.tpl

so it is reachable general from the whole website, and the dropzone-factory can use
it also to create dropzones from modal.js

src/Module/Post/Edit.php

@@ -185,8 +185,6 @@ class Edit extends BaseModule
 
 			'$compose_link_title' => $this->t('Open Compose page'),
 
-			// Dropzone
-			'$max_imagesize'       => round(Strings::getBytesFromShorthand(DI::config()->get('system', 'maximagesize')) / 1000000,1),
 		]);
 		return $output;
 	}