Update REMS glossary

[aatkin]

• applying users: #{:applicant :member} roles
• handling users: #{:handler :reviewer :decider :past-reviewer :past-decider} roles
• missing events: for example #{:application.event/voted :application.event/attachments-redacted}

Copy-paste from board note (removed old note in the process):

glossary.md is missing at least category and organization