upgrade dependencies for demo

demo/package.json

   },
   "dependencies": {
     "react": "16.8.3",
-    "react-native": "0.59.4",
+    "react-native": "0.59.8",
     "react-native-autoheight-webview": "../",
-    "react-native-webview": "5.6.2"
+    "react-native-webview": "^5.11.0"
   },
   "devDependencies": {
     "@babel/core": "^7.0.0",