Change cover image on oss related posts

Change cover image on open source related posts (hacktoberfest and  preptember posts) and also post that have a "variados" or "miscellaneous" cover image that have to do with open source 

This is the url for open source cover: https://res.cloudinary.com/jesstemporal/image/upload/v1760702982/covers/opensource_p4btht.png