Update readme with Invisible reCAPTCHA

README.md

@@ -84,6 +84,14 @@ With [custom attributes](https://developers.google.com/recaptcha/docs/display#re
 {!! NoCaptcha::display(['data-theme' => 'dark']) !!}
 ```
 
+Invisible reCAPTCHA using a [submit button](https://developers.google.com/recaptcha/docs/invisible):
+
+```php
+{!! NoCaptcha::displaySubmit('my-form-id', 'submit now!', ['data-theme' => 'dark']) !!}
+```
+Notice that the id of the form is required in this method to let the autogenerated 
+callback submit the form on a successful captcha verification.
+
 #### Validation
 
 Add `'g-recaptcha-response' => 'required|captcha'` to rules array :