fix: add Next.js v15 a possible peer dependency (#12098)

Allow Next.js 15

Author: thomaslindstrom

packages/next-auth/package.json

@@ -100,7 +100,7 @@
   },
   "peerDependencies": {
     "@auth/core": "0.34.2",
-    "next": "^12.2.5 || ^13 || ^14",
+    "next": "^12.2.5 || ^13 || ^14 || ^15",
     "nodemailer": "^6.6.5",
     "react": "^17.0.2 || ^18",
     "react-dom": "^17.0.2 || ^18"