fix: docusaurus/website/package.json & docusaurus/website/yarn.lock to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-SERIALIZEJAVASCRIPT-15809196

Author: snyk-io[bot]

docusaurus/website/package.json

@@ -6,8 +6,8 @@
     "deploy": "docusaurus deploy"
   },
   "dependencies": {
-    "@docusaurus/core": "^2.0.0-alpha.64",
-    "@docusaurus/preset-classic": "^2.0.0-alpha.64",
+    "@docusaurus/core": "^3.6.0",
+    "@docusaurus/preset-classic": "^3.6.0",
     "clsx": "^1.1.1",
     "react": "^16.12.0",
     "react-dom": "^16.12.0"