Merge pull request #896 from JuliaRobotics/22Q3/docs/ros_typegen

Update using_ros.md

Author: dehann

docs/src/examples/using_pcl.md

@@ -1,6 +1,6 @@
-# Pointclouds and PCL Types
+# [Pointclouds and PCL Types](@id pointclouds_and_pcl)
 
-## Introduction Caesar._PCL
+## Introduction `Caesar._PCL`
 
 A wide ranging and well used [point cloud library exists called PCL](https://pointclouds.org/) which is implemented in C++.  To get access to many of those features and bridge the Caesar.jl suite of packages, the base `PCL.PointCloud` types have been implemented in Julia and reside under `Caesar._PCL`.  The main types of interest:
 - [`Caesar._PCL.PointCloud`](@ref),

docs/src/examples/using_ros.md

@@ -53,10 +53,21 @@ Distributed.@everywhere using PyCall
 
 Caesar.jl has native by optional package tools relating to RobotOS.jl (leveraging [Requires.jl](https://github.com/JuliaPackaging/Requires.jl)):
 ```julia
-using RobotOS, Caesar
-Distributed.@everywhere using Caesar
+using RobotOS
+
+@rosimport sensor_msgs.msg: PointCloud2
+
+rostypegen()
+
+using Colors, Caesar
+Distributed.@everywhere using Colors, Caesar
 ```
 
+Colors.jl is added as a conditional requirement to get `Caesar._PCL.PointCloud` support ([see PCL page here](@ref pointclouds_and_pcl)).
+
+!!! note
+    Imports and type generation is necessary for RobotOS and Caesar to work properly.
+
 ## Prepare Any Outer Objects
 
 Usually a factor graph or detectors, or some more common objects are required.  For the example lets just say a basic SLAMWrapper containing a regular `fg=initfg()`: