Handle more S3 providers?

[gleepwurp]

Hi Greg,

I'm reaching out to see if you're interested into adding more s3 providers into your aws-s3-backup repo?

I've already cloned your repo and all your wonderful work, and I have adapted it to include WASABI as an s3 provider. If this repo is something you want to keep pushing forward, then I'll make a PR to you to contribute to it.

or, if you want to keep it AWS-centric, I can respect that and will leave it be.

Thanks, and nice work, it was just what I was looking for!

G.