update font awesome version (#304)

layouts/_default/baseof.html

@@ -22,7 +22,7 @@
     {{ end }}
 
     <link href="https://fonts.googleapis.com/css?family=Lato:400,700%7CMerriweather:300,700%7CSource+Code+Pro:400,700&display=swap" rel="stylesheet">
-    <link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.11.2/css/all.css" integrity="sha384-KA6wR/X5RY4zFAHpv/CnoG2UW1uogYfdnP67Uv7eULvTveboZJg0qUpmJZb5VqzN" crossorigin="anonymous" />
+    <link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.13.0/css/all.css" integrity="sha384-Bfad6CLCknfcloXFOyFnlgtENryhrpZCe29RTifKEixXQZ38WheV+i/6YWSzkz3V" crossorigin="anonymous">
     <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/normalize/8.0.1/normalize.min.css" integrity="sha256-l85OmPOjvil/SOvVt3HnSSjzF1TUMyT9eV0c2BzEGzU=" crossorigin="anonymous" />
 
     {{ if .Site.IsServer }}