添加站内消息，修复讨论节点丢失的问题

hydro/lib/markdown.js

@@ -1,15 +1,19 @@
-const hljs = require('highlight.js');
 const MarkdownIt = require('markdown-it');
 const katex = require('markdown-it-katex');
+const Prism = require('prismjs');
+const loadLanguages = require('prismjs/components/');
+
+// FIXME doesnt work in webpack
+loadLanguages(['js', 'javascript', 'go', 'c', 'pascal', 'hs', 'java', 'cs', 'cpp', 'py', 'ruby']);
 
 class Markdown extends MarkdownIt {
     constructor() {
         super({
             linkify: true,
             highlight(str, lang) {
-                if (lang && hljs.getLanguage(lang)) {
+                if (lang && Prism.languages[lang]) {
                     try {
-                        return hljs.highlight(lang, str).value;
+                        return Prism.highlight(str, Prism.languages[lang], lang);
                     } catch (__) { } // eslint-disable-line no-empty
                 }
                 return '';