fix(package): update styled-components to version 5.1.0

Closes #12

Author: greenkeeper[bot]

package.json

@@ -8,7 +8,7 @@
     "react": "^16.4.2",
     "react-dom": "^16.4.2",
     "react-scripts": "3.1.0",
-    "styled-components": "^4.0.2"
+    "styled-components": "^5.1.0"
   },
   "scripts": {
     "start": "react-scripts start",