[IDEA] Support for s3

[supercoolspy]

I'd be willing to help implement this but s3 support would be great since cloudflare has pretty much free s3 storage through r2

[DVDishka]

I'm finishing with google drive implementation and I can start with s3 support after that. If you really want to try to help me and add s3 support by yourself I can give you some advices how to implement it into the backuper