Update dependency react-native to v0.81.4

Author: mend-5034428[bot]

example/package.json

@@ -8,7 +8,7 @@
   },
   "dependencies": {
     "react": "16.6.1",
-    "react-native": "0.57.7",
+    "react-native": "0.81.4",
     "react-native-image-picker": "file:../"
   },
   "devDependencies": {