message: chore: add as a backup reviewer
diff: -# Eliza should review everything unassigned.
  -* @hawkw @tokio-rs/tracing
  +# Eliza should review everything unassigned, with David as a backup.
  +* @hawkw @davidbarsky @tokio-rs/tracing
  # tracing-core should include Eliza and Carl.
  /tracing-core/ @hawkw @carllerche
  