Github sponsors support

GitHub is rolling out their sponsors program.

Adding a check with github's api to see if found developers have sponsorships enabled would save them having to know about this project.

If the idea appeals, I might look into implementing it in the near future.

After checking, I've found no way yet within the github api to receive the sponsor list for a repository or user.

This is a cool idea. PR welcome!

Another note to self

There's a multiple routes this can take:

• Without repository in package.json
  • See if there's a .github/FUNDING.yml in the package (for when they don't .npmignore it)
• Requires repository url in package.json
  • Fetch the funding.yml from the repository on github & parse that to generate funding urls
  • Fetch contributors through graphql api & see if they have anything listed using the sponsorable interface.