bump: nextjs to react 19

Author: echarles

examples/next-js/package.json

@@ -14,8 +14,8 @@
     "@datalayer/primer-addons": "^1.0.0",
     "next": "^15.4.1",
     "next-themes": "^0.4.6",
-    "react": "^18.2.0",
-    "react-dom": "^18",
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0",
     "svg-url-loader": "^8.0.0"
   },
   "devDependencies": {