Updates repository URL

[curran]

This is quite a useful change, and would resolve doubts/tensions in the following threads:

• https://github.com/FredKSchott/rollup-plugin-polyfill-node/issues/41
• https://github.com/rollup/rollup/issues/2881
• https://github.com/rollup/plugins/pull/51#issuecomment-747489334

It would be great to make it so that the NPM page for this package links into this repo.

LGTM!

[curran]

Hooray! Thank you @FredKSchott 🙏