Add ckeditor3 to security-support-ended.12 and security-support-ended.11
security-support-ended.12: see confirmation from @jmm:
See https://lists.debian.org/debian-lts/2025/04/msg00011.html
security-support-ended.11: @santiago do you confirm for bullseye-lts?
https://lists.debian.org/debian-lts/2025/04/msg00009.html