update react-scripts to 3.1.0

package.json

@@ -39,7 +39,7 @@
     "react-rnd": "^7.4.3",
     "react-router": "^4.3.1",
     "react-router-dom": "^4.3.1",
-    "react-scripts": "^1.1.5",
+    "react-scripts": "^3.0.1",
     "react-sortable-tree": "^0.1.19",
     "react-svg-pan-zoom": "^2.18.0",
     "superagent": "^3.8.3",
@@ -54,5 +54,17 @@
     "test": "react-scripts test --env=jsdom",
     "eject": "react-scripts eject"
   },
-  "proxy": "http://localhost:4000"
+  "proxy": "http://localhost:4000",
+  "browserslist": {
+    "production": [
+      ">0.2%",
+      "not dead",
+      "not op_mini all"
+    ],
+    "development": [
+      "last 1 chrome version",
+      "last 1 firefox version",
+      "last 1 safari version"
+    ]
+  }
 }