[BTS] Create buster usertags sort

[Niels Thykier]

# https://wiki.debian.org/Teams/ReleaseTeam/ReleaseCheckList
user release.debian....@packages.debian.org
usercategory buster-sort
  * Codename [tag=]
    + Blockers for Codename [buster-is-blocker]
    + Planned for removal [buster-will-remove]
    + Ignored for Codename [buster-can-defer]
thanks