Add attic

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

packages/docker/attic/entrypoint.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env sh
+
+set -o errexit
+set -o nounset
+
+atticd "$@" &
+PID=$!
+
+if [ -f /etc/attic/post-start.sh ]; then
+  # shellcheck disable=SC1091
+  . /etc/attic/post-start.sh
+fi
+
+trap 'kill -KILL "$PID"' INT TERM
+wait "$PID"
+exit $?