Document population-based training workflow

Author: ooctipus

docs/index.rst

@@ -137,7 +137,6 @@ Table of Contents
    source/features/docker_cloud
    source/features/hydra
    source/features/multi_gpu
-   source/features/population_based_training
    source/features/ray
    source/features/reproducibility
 

docs/source/features/population_based_training.rst

@@ -3,12 +3,13 @@ Reinforcement Learning
 
 Isaac Lab supports multiple reinforcement learning frameworks.
 In this section, we show existing scripts for running reinforcement learning
-with supported RL libraries and provide a comparison of the supported
-learning frameworks.
+with supported RL libraries, compare the supported learning frameworks, and
+cover training and optimization workflows.
 
 .. toctree::
   :maxdepth: 1
 
   rl_existing_scripts
   rl_frameworks
   training_guide
+  population_based_training