G-recaptcha tag attribute "data-callback"

Hi.
We've faced with an issue with iOS. In short, when the image challenge appears, the page is being scrolled to the bottom. This is a known reCAPTCHA issue and it was described here:
https://github.com/google/recaptcha/issues/130
One of solutions is to scroll the page back manually. To do it, by reference we need to have a g-recaptcha's data-callback attribute:
https://developers.google.com/recaptcha/docs/display#render_param
It is also used in the "Invisible reCAPTCHA".
Here is a patch to add the configuration of this attribute to the module.