Validator: Allow for custom types to be added to Validator instance about php7-common

[cdtweb]

Custom type can be added using the addType method:

<?php
use Noname\Common\Validator;

$values = ['a' => 2];
$rules = ['a' => ['type' => 'equals_2']];
$validator = new Validator();
$validator->addType('equals_2', [
    'extends' => 'numeric',
    'validator' => function ($value, $rule, $validator) {
        $valid = $value === 2;
        if (!$valid) {
            $validator->setError($rule['name'], 'Value does not equal 2');
        }
        return $valid;
    }
]);
$validator->validate();