Execute ros launch at startup

[Tiryoh]

According to the following issue comment, there is a way to execute command on startup.

fcwu/docker-ubuntu-vnc-desktop#85 (comment)

It may be useful to have a program such as Gazebo start automatically when opening a web browser.

[Tiryoh]

Running the container with the OPENBOX_ARGS worked.

docker run -p 6080:80 --shm-size=512m -e OPENBOX_ARGS='--startup "/usr/bin/gazebo"' tiryoh/ros-desktop-vnc:melodic

However, sometimes Gazebo would not start and I had to access http://127.0.0.1:6080/resize.