Add custom data field in uploader and use it in the image lightbox

Hi !
I have added a custom field in the rtmedia uploader (called "city"), and I would like this field to be displayed in the lightbox, after the image upload, so that we can see in the lighbox the city writen by the user.

I know that I need to modify media-single.php for the layout, but I don't know how to get the field
from the uploader in order to use it in media-single.php

Here is the code added in functions.php:

function custom_data() {
        global $rtmedia_media;
        ?>  <div> city :<input class="city" id="city" type="text" name="city" value="" /> </div>
        <?php
        }
        
add_action('rtmedia_uploader_before_start_upload_button', 'custom_data');

I have also seen this topic but I really don't know what code I should put in the Ajax hook request..:

Thanks a lot for your help!
Marine