add ustc font cdn

layout/_partial/cdn_head.ejs

@@ -1,6 +1,9 @@
 <% if (theme.cdn == "useso"){ %>
  <link href='//fonts.useso.com/css?family=Open+Sans:400italic,400,600' rel='stylesheet' type='text/css'>
  <link href="//fonts.useso.com/css?family=Source+Code+Pro" rel="stylesheet" type="text/css">
+<% } else if (theme.cdn == "ustc") { %>
+ <link href='//fonts.lug.ustc.edu.cn/css?family=Open+Sans:400italic,400,600' rel='stylesheet' type='text/css'>
+ <link href="//fonts.lug.ustc.edu.cn/css?family=Source+Code+Pro" rel="stylesheet" type="text/css">
 <% } else { %>
  <link href='https://fonts.googleapis.com/css?family=Open+Sans:400italic,400,600' rel='stylesheet' type='text/css'>
  <link href='https://fonts.googleapis.com/css?family=Source+Code+Pro' rel='stylesheet' type='text/css'>