markdown语法增强，错误修复

package.json

@@ -17,7 +17,11 @@
         "koa-static-cache": "^5.1.3",
         "lodash": "^4.17.15",
         "markdown-it": "^10.0.0",
+        "markdown-it-container": "^3.0.0",
+        "markdown-it-footnote": "^3.0.2",
+        "markdown-it-imsize": "^2.0.1",
         "markdown-it-katex": "^2.0.3",
+        "markdown-it-mark": "^3.0.0",
         "moment-timezone": "^0.5.31",
         "mongodb": "^3.5.7",
         "nodemailer": "^6.3.1",