Add default value for flags in help message

[jinyus]

app.add_flag(cli.Flag{
	flag: .bool
	name: 'verbose'
	default_value: ['false']
	description: 'verbosely list files processed being processed'
})

it would be useful to include the default value in the help message

Flags:
-verbose          verbosely list files being processed **(defaults to false)**<- this should be included
-help             Prints help information.

Commands:
help                Prints help information.

[MaxPaw]

There is (required) if option is required, seems like (default: 123) should be added as well