Bump react-modal from 3.2.1 to 3.3.1 in /www (#866)

Bumps [react-modal](https://github.com/reactjs/react-modal) from 3.2.1 to 3.3.1.
- [Changelog](https://github.com/reactjs/react-modal/blob/master/CHANGELOG.md)
- [Commits](reactjs/react-modal@v3.2.1...v3.3.1)

www/package.json

@@ -121,7 +121,7 @@
     "react-dom": "^16.2.0",
     "react-feather": "1.0.8",
     "react-helmet": "^5.2.0",
-    "react-modal": "^3.2.1",
+    "react-modal": "^3.3.1",
     "react-qr-svg": "^2.1.0",
     "react-redux": "^5.0.7",
     "react-router-dom": "^4.2.2",

www/yarn.lock

@@ -7162,9 +7162,9 @@ react-hot-loader@^3.1.3:
     redbox-react "^1.3.6"
     source-map "^0.6.1"
 
-react-modal@^3.2.1:
-  version "3.2.1"
-  resolved "https://registry.yarnpkg.com/react-modal/-/react-modal-3.2.1.tgz#fa8f76aed55b67c22dcf1a1c15b05c8d11f18afe"
+react-modal@^3.3.1:
+  version "3.3.1"
+  resolved "https://registry.yarnpkg.com/react-modal/-/react-modal-3.3.1.tgz#7355db196482da0c7fa1cbecccf2bdd9bc366b14"
   dependencies:
     exenv "^1.2.0"
     prop-types "^15.5.10"