New tutorial - "Setup custom domain with S3-compatible object storage"

[ivan-zaitsev]

Tutorial shows how to setup custom domain with S3-compatible object storage using a reverse proxy.

At the time of writing this tutorial custom domain using CNAME is not available, and reverse proxy is the only way.

I have read and understood the Contributor's Certificate of Origin available at the end of 
https://raw.githubusercontent.com/hetzneronline/community-content/master/tutorial-template.md
and I hereby certify that I meet the contribution criteria described in it.
Signed-off-by: Ivan Zaitsev https://github.com/ivan-zaitsev

[svenja11]

Thank you for your contribution @ivan-zaitsev