Move the new mirror pool design doc to contribute/design
Originally created by @intrigeri on #11902 (Redmine)
Blueprint: https://tails.boum.org/blueprint/HTTP_mirror_pool/
Parent Task: #7161 (closed)
Originally created by @intrigeri on #11902 (Redmine)
Blueprint: https://tails.boum.org/blueprint/HTTP_mirror_pool/
Parent Task: #7161 (closed)