Github sponsors support

GitHub is rolling out their sponsors program.

Adding a check with [github's api](https://developer.github.com/v4/object/user/) 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.

The issue points to GitHub's GraphQL User object documentation, but names no repository files, tests, or entry points. Start by locating the existing developer lookup and output flow, then determine how sponsorship status should be represented; done would mean the project checks the GitHub API and surfaces enabled sponsorships without requiring users to know about the program.

Written by the indexing model from the issue text.