fix: package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-POSTCSS-5926692

Author: snyk-bot

package.json

@@ -24,7 +24,7 @@
     "lodash": "^4.17.20",
     "moment": "^2.29.1",
     "moment-timezone": "^0.5.33",
-    "next": "^12.0.5",
+    "next": "^13.5.4",
     "next-compose-plugins": "^2.2.1",
     "next-i18next": "^8.5.5",
     "next-seo": "^4.17.0",