Create a Schleuder mailing list for manual testers
_Originally created by @intrigeri on [#17416 (Redmine)](https://public-redmine-archive.tails.boum.org/code/issues/17416)_
This would simplify the RM’s life:
- Every individual RM does not need to maintain the corresponding
keyring on their own locally.
- It allows the RM to reply to the previous message they’ve sent to
testers (there are 2 such messages during 1 release process).
It could be called tails-manual-testers@boum.org.
List admins should be kibi (primary RM) and anonym (secondary RM).
### Related issues
- **Related to** tails/tails#17361
issue