Support new check runs

[dereuromark]

I currently implemented this for us, since the former statuses kind of don't work anymore since 1st of October (deprecated).

    /**
     * @param string $organization
     * @param string $repository
     * @param string $sha
     * @param array $params
     * @return mixed
     */
    public function checkRuns(string $organization, string $repository, string $sha, array $params = []): array
    {
        $url = 'repos/' . rawurlencode($organization) . '/' . rawurlencode($repository) . '/commits/' . $sha . '/check-runs';

        $headers = [
            'Accept' => 'application/vnd.github.antiope-preview+json',
        ];

        return $this->get($url, $params, $headers);
    }

Would be nice if this repo ships with native support for the new API.

[acrobat]

I'm tagging this as a feature-request. Feel free to create a PR for it or otherwise I will pick it up when I find some time!

[acrobat]

Added in #788