Update url-loader to 0.6.2 for mime ReDoS vuln (facebook#3246)

- Changelog: https://github.com/webpack-contrib/url-loader/blob/master/CHANGELOG.md
 - Reference issue:  https://nodesecurity.io/advisories/535

Fixes facebook#3244

Author: joshwiens

package.json

@@ -51,7 +51,7 @@
     "react-dev-utils": "^4.1.0",
     "style-loader": "0.18.2",
     "sw-precache-webpack-plugin": "0.11.4",
-    "url-loader": "0.5.9",
+    "url-loader": "0.6.2",
     "webpack": "3.5.1",
     "webpack-dev-server": "2.8.2",
     "webpack-manifest-plugin": "1.2.1",