README cosmetic issue: `cmdargs` vs. `cmdargs`

[netgab]

Hi there,

The programmatic usage example in the README is not valid for IOS / IOS-XE devices.

The example for command authorization ([b"service=shell", b"cmd=show", b"cmdargs=version"]) is using the key cmdargs.
However, Cisco Devices use the key cmd-arg for command authorization.

So the correct example would be: [b"service=shell", b"cmd=show", b"cmd-arg=version"]

Furthermore an example for a command with more than two words would be helpful.
Example: show interfaces Vlan 20 summary

=> [b"service=shell", b"cmd=show", b"cmd-arg=interfaces", b"cmd-arg=vlan", b"cmd-arg=20", b"cmd-arg=summary"]