feat(docker): add docker functionality.

docker/docker-entrypoint.d/00-preflight.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+
+set -e
+
+[ -z "$DEBUG" ] || set -x
+
+if [ ! -f /app/bumblebee ]; then
+  echo "$0: /app/bumblebee not found, I can't start!!"
+  exit 1
+fi

docker/docker-entrypoint.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+
+set -e
+
+for file in /docker-entrypoint.d/*; do
+  echo "$0: running $file"
+  sh "$file"
+done
+
+cd /app
+exec ./bumblebee