Filter the point cloud data

[katie-hughes]

I created a simple node and I included PCL. This repository contains a bag file of lidar data that I can practice processing. The general pipeline I am following is:

• subscribe to /rslidar_points (the point cloud data)
• convert ros message type to pcl type (this is done via pcl_convert, similarly to this example: https://github.com/GitRepJo/pcl_example/blob/main/src/pcl_example.cpp)
• use builtin pcl function to filter based on region (this will be similar to what I'm doing with people detection). I think this function is exactly what I want: https://pointclouds.org/documentation/classpcl_1_1_conditional_removal.html#details
• Convert back to ros message type and publish. Then this can be what is sent back through the nav2 pipeline.