fix: package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-QS-14724253

Author: snyk-bot

package.json

@@ -10,7 +10,7 @@
   },
   "dependencies": {
     "@nuxt/content-theme-docs": "^0.11.0",
-    "nuxt": "^2.15.8",
+    "nuxt": "^3.0.0",
     "vue-gtag": "^1.16.1"
   }
 }