chore: Add docker label

[Tiryoh]

close #37

$ docker inspect tiryoh/ros2-desktop-vnc:foxy | jq ".[0].Config.Labels"
{
  "maintainer": "Tiryoh<*****@gmail.com>",
  "org.opencontainers.image.created": "2022-01-16T09:34:17.340Z",
  "org.opencontainers.image.description": "Dockerfiles to provide HTML5 VNC interface to access Ubuntu LXDE + ROS2",
  "org.opencontainers.image.licenses": "Apache-2.0",
  "org.opencontainers.image.revision": "d18f594c61363fefaf088d79d91b24006d9e41a7",
  "org.opencontainers.image.source": "https://github.com/Tiryoh/docker-ros2-desktop-vnc",
  "org.opencontainers.image.title": "docker-ros2-desktop-vnc",
  "org.opencontainers.image.url": "https://github.com/Tiryoh/docker-ros2-desktop-vnc",
  "org.opencontainers.image.version": "foxy-arm64-20220116T0934"
}