Sourcery doesn't report status checks on GitHub

[br3ndonland]

Description

I opened a PR today (br3ndonland/inboard#43), expecting to receive a report from the Sourcery GitHub App. It didn't show up until after I merged the PR.

It would be helpful to have Sourcery provide status checks, so users know when they should wait for a result.

Suggestions

• Use the GitHub Checks API to report the status of Sourcery analysis and refactorings, like Codecov does
• Provide Sourcery configuration settings to configure checks