Flag if a sitemap is not submitted in GSC#313

I’ve seen it already (rookie mistake) that some domain owner forget submitting their XML sitemap in GSC. This should be flagged as a critical error IMO

@Jonathan Bluemel good idea! I didn’t have idea for a long time how to implement this check but looks like that this API can help us - https://developers.google.com/webmaster-tools/v1/sitemaps/list