doc: add a CLI example

Author: oesteban

docs/cli.rst

@@ -4,3 +4,12 @@ Using the client with the Command-line interface (CLI)
 .. click:: templateflow.cli:main
   :prog: templateflow
   :nested: full
+
+Examples
+--------
+Listing all the compressed NIfTI files in ``fsaverage``::
+
+	$ templateflow ls fsaverage -x .nii.gz
+	~/.cache/templateflow/tpl-fsaverage/tpl-fsaverage_res-01_den-41k_T1w.nii.gz
+	~/.cache/templateflow/tpl-fsaverage/tpl-fsaverage_res-01_desc-brain_mask.nii.gz
+	~/.cache/templateflow/tpl-fsaverage/tpl-fsaverage_res-01_T1w.nii.gz