Add core-js as dependency as a temporary fix

Temporary fix for: #6
Which is caused by: pastelsky/package-build-stats#37
Which is caused by: zoobestik/csso-webpack-plugin#28

Author: rafgraph

package-lock.json

@@ -46,6 +46,7 @@
     "@typescript-eslint/eslint-plugin": "^4.18.0",
     "@typescript-eslint/parser": "^4.18.0",
     "chalk": "^4.1.0",
+    "core-js": "^3.10.0",
     "eslint": "^7.22.0",
     "eslint-config-prettier": "^8.1.0",
     "eslint-plugin-import": "^2.22.1",