fix: web app manifest link

Fix #1245

layouts/slides/baseof.html

@@ -9,7 +9,7 @@
   <meta http-equiv="X-UA-Compatible" content="IE=edge">
   <meta name="generator" content="Source Themes Academic {{ site.Data.academic.version }}">
 
-  <link rel="manifest" href="{{ "site.webmanifest" | relURL }}">
+  <link rel="manifest" href="{{ "index.webmanifest" | relURL }}">
   <link rel="icon" type="image/png" href="{{ "/img/icon.png" | relURL }}">
   <link rel="apple-touch-icon" type="image/png" href="{{ "/img/icon-192.png" | relURL }}">