fix: cjk support + demo page

layouts/partials/katex.html

@@ -5,15 +5,12 @@
 <script>
   document.addEventListener("DOMContentLoaded", function() {
     renderMathInElement(document.body, {
-      // customised options
-      // • auto-render specific keys, e.g.:
       delimiters: [
         {left: '$$', right: '$$', display: true},
         {left: '$', right: '$', display: false},
         {left: '\\(', right: '\\)', display: false},
         {left: '\\[', right: '\\]', display: true}
       ],
-      // • rendering keys, e.g.:
       throwOnError : false
     });
   });