重构框架，增加比赛功能

hydro/lib/markdown.js

@@ -0,0 +1,22 @@
+const
+    hljs = require('highlight.js'),
+    MarkdownIt = require('markdown-it'),
+    katex = require('markdown-it-katex');
+
+class Markdown extends MarkdownIt {
+    constructor() {
+        super({
+            linkify: true,
+            highlight: function (str, lang) {
+                if (lang && hljs.getLanguage(lang))
+                    try {
+                        return hljs.highlight(lang, str).value;
+                    } catch (__) { } // eslint-disable-line no-empty
+                return '';
+            }
+        });
+        this.linkify.tlds('.py', false);
+        this.use(katex);
+    }
+}
+module.exports = new Markdown();