docs: Added CLI documentation (#444)

* Document the CLI parameters and default values
* Use markdown when printing CLI help
* Print parameter's required, optional and defaults fields
* tests for default parameter values and formatting
* Added "CLI Command Reference" page to the documentation

Closes #228 and
#382

---------

Signed-off-by: Ahmad Kiswani <kiswani.ahmad@gmail.com>
Signed-off-by: Lawrence Lane <llane@nvidia.com>
Co-authored-by: Lawrence Lane <llane@nvidia.com>

Author: ahmadki

docs/index.md

@@ -163,6 +163,13 @@ tutorials/rl-training-with-nemo-rl
 how-to-faq.md
 ```
 
+```{toctree}
+:caption: Reference
+:hidden:
+:maxdepth: 1
+
+reference/cli-commands.md
+```
 
 ```{toctree}
 :caption: Development