Use official Web App Manifest extension

index.html

@@ -24,7 +24,7 @@
 		<!-- <link rel="icon" type="image/png" sizes="16x16" href="images/icons/16x16.png"> -->
 		<link rel="shortcut icon" href="favicon.ico">
 		<link rel="mask-icon" href="images/icons/safari-pinned-tab.svg" color="red">
-		<link rel="manifest" href="manifest.webapp">
+		<link rel="manifest" href="manifest.webmanifest">
 		<meta name="msapplication-TileColor" content="#ffffff">
 		<meta name="msapplication-TileImage" content="images/icons/ms-icon-144x144.png">
 		<meta name="theme-color" content="#008080">