`multipass stop` command

Following topic is created to add in the documentation section the help for the stop command.
(based on the comment here)

Usage: multipass stop [options] [ …]
Stop the named instances, if running. Exits with return code 0 if successful.

Options:
  -h, --help         Display this help
  -v, --verbose      Increase logging verbosity. Repeat the 'v' in the short option for more detail.  
                 Maximum verbosity is obtained with 4 (or more) v's, i.e. -vvvv.
  --all              Stop all instances
  -t, --time <time>  Time from now, in minutes, to delay shutdown of the
                     instance
  -c, --cancel       Cancel a pending delayed shutdown

Arguments:
  name               Names of instances to stop. If omitted, and without the
                     --all option, 'primary' will be assumed

@saviq, let me know if the quality of the post above is sufficient enough for the documentation to be improved. I’ll proceed asap for the other topics I can create.