Move polyfill to CDN section

We don't support it on CDN false instances, but it doesn't hurt to keep
it in for CDN-enabled instances

Signed-off-by: Sheogorath <sheogorath@shivering-isles.com>

public/views/hackmd/head.ejs

@@ -15,8 +15,8 @@
 <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/octicons/3.5.0/octicons.min.css" integrity="sha256-QiWfLIsCT02Sdwkogf6YMiQlj4NE84MKkzEMkZnMGdg=" crossorigin="anonymous" />
 <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/emojify.js/1.1.0/css/basic/emojify.min.css" integrity="sha256-UOrvMOsSDSrW6szVLe8ZDZezBxh5IoIfgTwdNDgTjiU=" crossorigin="anonymous" />
 <%- include ../build/index-header %>
+<%- include ../shared/polyfill %>
 <% } else { %>
 <link rel="stylesheet" href='<%- url %>/build/emojify.js/dist/css/basic/emojify.min.css'>
 <%- include ../build/index-pack-header %>
 <% } %>
-<%- include ../shared/polyfill %>