Upgrade docusaurus to 2.4

Author: HeikoBornholdt

package.json

@@ -14,8 +14,8 @@
     "write-heading-ids": "docusaurus write-heading-ids"
   },
   "dependencies": {
-    "@docusaurus/core": "^2.3.0",
-    "@docusaurus/preset-classic": "^2.3.0",
+    "@docusaurus/core": "^2.4.0",
+    "@docusaurus/preset-classic": "^2.4.0",
     "@easyops-cn/docusaurus-search-local": "^0.33.6",
     "@mdx-js/react": "^1.6.22",
     "clsx": "^1.2.1",