title: Formly Email custom validation with pattern does not works
body: <p>I want to validate input (email) in ngx-formly. tried with the code below but it dint worked</p>
  <p>app.module.ts</p>
  <pre><code>export function EmailValidator(control: FormControl): ValidationErrors {
      return /^[a-z0-9._%+-]+@[a-z0-9.-]+\\.[a-z]{2,4}$/.test(control.value) ? null : { 'email': true };
  }
  
  export function EmailValidatorMessage(err, field: FormlyFieldConfig) {
      return `&quot;${field.formControl.value}&quot; is not a valid Email Address`;
  }
  </code></pre>
  <p>app.component.ts</p>
  <pre><code>{
      key: 'email',
      type: 'input',
      className: 'flex-3',
      templateOptions: {
          type: 'text',
          label: 'Email',
          placeholder: 'Email',
      },
      validators: {
          validation: ['email'],
      }
  }
  </code></pre>