Link image to after uploading to /wp/v2/media (do an action after attachment has been inserted, use $request parameters)

customize.rest.api.php

<?php
add_action('rest_insert_attachment', function($attachment, $request, $creating) {
  $data = $request->get_params(); // Extra data that was sent to /wp/v2/media 
  // In this example we can use $data['entry_id']
  // Something like: update_post_meta((int) $data['entry_id'], 'attachment_id', $attachment['ID']);
});

include.script.php

<?php
// Include jQuery and wp-api
add_action('wp_enqueue_script', function()) {
  wp_enqueue_script('upload-', plugin_dir_url(__FILE__).'assets/js/script.js', array('jquery', 'wp-api'));
});
?>

prepare.formdata.js

var file = ''; // your filelist from file input
var entry_id = 0 // some data to attach

// Prepare the form element
var formData = new FormData();
formData.append( 'file', file ); // probably should pick a file to upload
formData.append( 'entry_id', entry_id ); // 

jQuery.ajax({
  url: wpApiSettings.root + 'wp/v2/media',
  method: 'POST',
  processData: false,
  contentType: false,
  beforeSend: function(xhr) {
    xhr.setRequestHeader( 'X-WP-Nonce', wpApiSettings.nonce );
  },
  data: formData,
  success: function(data) {
    console.log(data)
  }
})