README gives the false impression that conversion from Pointcloud2 to grid_map layers are available.

[cemonem]

Hello,

The Readme gives the false impression that there are seamless methods of conversion available for using pointcloud messages. This issue #158 suggests that is not the case, there are some workarounds with converting to octomap then grid_map or heavy lifting needs to be done by porting elevation mapping code from ROS1 to ROS2. Please update the README.

Thanks.