fix: upgrade multiple dependencies with Snyk

Snyk has created this PR to upgrade:
  - react from 16.8.6 to 16.13.0.
    See this package in NPM: https://www.npmjs.com/package/react
  - react-dom from 16.8.6 to 16.13.0.
    See this package in NPM: https://www.npmjs.com/package/react-dom

See this project in Snyk:
https://app.snyk.io/org/willemliufdmg/project/30488acc-1abe-4af1-b1dd-b2cb5474eb30?utm_source=github&utm_medium=upgrade-pr

Author: snyk-bot

package-lock.json

@@ -61,8 +61,8 @@
         "webpack-cli": "^3.3.6"
     },
     "dependencies": {
-        "react": "^16.8.6",
-        "react-dom": "^16.8.6",
+        "react": "^16.13.0",
+        "react-dom": "^16.13.0",
         "styled-components": "^5.0.0-beta.6-ej4"
     },
     "jest": {