fix: upgrade core-js from 2.4.1 to 2.6.12

Snyk has created this PR to upgrade core-js from 2.4.1 to 2.6.12.

See this package in npm:
core-js

See this project in Snyk:
https://app.snyk.io/org/rajdeep-tg/project/168213bf-7a54-4af4-a7c1-a584b467b697?utm_source=github&utm_medium=referral&page=upgrade-pr

Author: snyk-bot