minor: Example readme update

Author: stephane-caron

examples/README.md

@@ -2,6 +2,8 @@
 
 ## Show all humanoid descriptions
 
+This example shows all humanoid robot descriptions using Pinocchio and MeshCat:
+
 ```
 python all_humanoids.py
 ```
@@ -10,6 +12,8 @@ python all_humanoids.py
 
 ## Show all quadruped descriptions
 
+This example shows all quadruped robot descriptions using Pinocchio and MeshCat:
+
 ```
 python all_quadrupeds.py
 ```