Update README.md

[adrianmatthews]

The following example code contains the jsOption 'allowExtensions'.
This should be removed because the autoFormat / allowExtensions / getExtension functionality was removed in v8.0.0.

use borales\extensions\phoneInput\PhoneInput;

echo PhoneInput::widget([
    'name' => 'phone_number',
    'jsOptions' => [
        'allowExtensions' => true,
        'onlyCountries' => ['no', 'pl', 'ua'],
    ]
]);