Allow altering captcha's markup attributes

Problem/Motivation

The module does not allow to alter the captcha markup configuration we can find on the official documentation.

For example, i need for a specific project to alter the https://docs.friendlycaptcha.com/#/widget_api?id=data-start-attribute to "none".

Proposed resolution

1. Add some options in the admin configuration form /admin/config/people/captcha/friendlycaptcha

2. or create a custom theme and template to render the captcha in friendlycaptcha_captcha() (its currently a simple #markup)

Thanks