Add link to 512px icon, fix missing link

src/App/Page.php

@@ -233,7 +233,7 @@ class Page implements ArrayAccess
 
 		$touch_icon = $config->get('system', 'touch_icon');
 		if ($touch_icon == '') {
-			$touch_icon = 'images/friendica-128.png';
+			$touch_icon = 'images/friendica-192.png';
 		}
 
 		Hook::callAll('head', $this->page['htmlhead']);

src/Module/Manifest.php

@@ -47,6 +47,11 @@ class Manifest extends BaseModule
 					'sizes' => '192x192',
 					'type'  => 'image/png',
 				],
+				[
+					'src'   => DI::baseUrl()->get() . '/' . $touch_icon,
+					'sizes' => '512x512',
+					'type'  => 'image/png',
+				],
 			],
 		];