Is your feature request related to a problem? Please describe.
Current validators of Jafar are defined by object, which is appropriate for designer and builder tools. But sometimes it is not for programmer.

Describe the solution you'd like
Shorthand definitions are necessary.

Describe alternatives you've considered
Moleculer has a validator, which support shorthand definitions.

const schema = {
    password: "string|min:6",
    age: "number|optional|integer|positive|min:0|max:99", // additional properties
    state: ["boolean", "number|min:0|max:1"] // multiple types
}