Requested feature overview description.
staging.cohostcdn.org should be added to the whitelisted upload domains.

Why would it be useful?
This would be so you can easily upload artwork from cohost.org.

What part(s) of the site page(s) are affected?
https://e621.net/upload_whitelists
https://e621.net/uploads/new

Additional Information
Any url from cohostcdn shouldn't include anything after the ? in the url as the artwork would be resized e.g. you could upload https://staging.cohostcdn.org/attachment/uuid/art.png but not http://staging.cohostcdn.org/attachment/uuid/art.png?dpr=1&width=628&height=436&fit=cover
cohost's terms of service can found here: https://cohost.org/rc/content/tos; Their community guidelines can be found here: https://cohost.org/rc/content/community-guidelines.