[doc] git submodule requires more workload.
[doc] git submodule requires more workload.

tecnalia-advancedmanufacturing-robotics/industrial_ci,geoffreychiou/industrial_ci,ros-industrial/industrial_ci,tecnalia-advancedmanufacturing-robotics/industrial_ci,geoffreychiou/industrial_ci,ros-industrial/industrial_ci,tecnalia-advancedmanufacturing-robotics/industrial_ci,ros-industrial/industrial_ci