添加站内消息，修复讨论节点丢失的问题

package.json

@@ -8,19 +8,19 @@
     "dependencies": {
         "axios": "^0.19.0",
         "bson": "^4.0.2",
-        "highlight.js": "^9.18.1",
         "js-yaml": "^3.13.1",
         "koa": "^2.11.0",
         "koa-body": "^4.1.1",
         "koa-morgan": "^1.0.1",
         "koa-router": "^8.0.8",
-        "koa-static-cache": "^5.1.2",
+        "koa-static-cache": "^5.1.3",
         "lodash": "^4.17.15",
         "markdown-it": "^10.0.0",
         "markdown-it-katex": "^2.0.3",
-        "mongodb": "^3.5.5",
+        "mongodb": "^3.5.7",
         "nodemailer": "^6.3.1",
         "nunjucks": "^3.2.1",
+        "prismjs": "^1.20.0",
         "sockjs": "^0.3.20"
     },
     "devDependencies": {
@@ -47,4 +47,4 @@
             "templates/*"
         ]
     }
-}
+}