message: [docker] add `zeroconf` in the docker image for OTBR CI
  `zeroconf` may be used for implementing mDNS browsers used by `node.py`.
diff: @@ -79,7 +79,7 @@ ENV OTBR_BUILD_DEPS apt-utils build-essential psmisc ninja-build cmake wget ca-c
  libnetfilter-queue-dev
  # Required for OpenThread Backbone CI
  -ENV OTBR_OT_BACKBONE_CI_DEPS curl lcov wget build-essential python3-dbus
  +ENV OTBR_OT_BACKBONE_CI_DEPS curl lcov wget build-essential python3-dbus python3-zeroconf
  # Required and installed during build (script/bootstrap) when RELEASE=1, could be removed
  ENV OTBR_NORELEASE_DEPS \
  