message: chore: add core-js as peer-dep
  fixes
diff: "mobx": "^4.2.0 || ^5.0.0",
  "react": "^16.8.4",
  "react-dom": "^16.8.4",
  - "styled-components": "^4.1.1"
  + "styled-components": "^4.1.1",
  + "core-js": "^2.6.5"
  },
  "dependencies": {
  "classnames": "^2.2.6",
  