add mobile viewport

templates/index.html

@@ -4,6 +4,10 @@
         <meta charset="UTF-8" />
         <title>Isotope</title>
         <link rel="stylesheet" type="text/css" href="/styles.css" />
+        <meta
+            name="viewport"
+            content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no"
+        />
     </head>
     <body>
         <div class="content">