NPM warning on core-js 2.6.11

(NPM version 6.14.3)

When installing `github-release-notes`, npm generates the following warning:
```
npm WARN deprecated core-js@2.6.11: core-js@<3 is no longer maintained and not recommended for usage due to the number of issues. Please, upgrade your dependencies to the actual version of core-js@3.

> core-js@2.6.11 postinstall /Volumes/Development/kiwidocs/node_modules/core-js
> node -e "try{require('./postinstall')}catch(e){}"

Thank you for using core-js ( https://github.com/zloirock/core-js ) for polyfilling JavaScript standard library!
```
So it appears that something needs updated to core-js 3 or better. I'm not sure if it is `github-release-notes` itself, or a dependency.

I'll add more once I've had a chance to probe further.