open fun registerCommand(command: Command): CommandRegistry
Like io.vertx.rxjava.ext.shell.command.CommandRegistry#registerCommand, without a completion handler.
Return
open fun registerCommand(command: Command, completionHandler: Handler<AsyncResult<Command>>): CommandRegistry
Register a command
command - the command to register
completionHandler - notified when the command is registered
Return
a reference to this, so the API can be used fluently