Fix typo in commands documentation

docs/ext/commands/commands.rst

@@ -5,7 +5,7 @@
 Commands
 ==========
 
-One of the most appealing aspect of the command extension is how easy it is to define commands and
+One of the most appealing aspects of the command extension is how easy it is to define commands and
 how you can arbitrarily nest groups and commands to have a rich sub-command system.
 
 Commands are defined by attaching it to a regular Python function. The command is then invoked by the user using a similar