The plugin provides drag’n’drop file uploads and uses the wp rest api to upload the file. BTW, I've written a similar plugin that uses the WordPress AJAX API for file uploads.
Save dropzonejs-wp-rest-api.php in wp-content/plugins/dropzonejs-wp-rest-api/
Save dropzonejs-wp-rest-api.js in wp-content/plugins/dropzonejs-wp-rest-api/js/
After activating the plugin, add the [dropzonerest] shortcode to a post
https://github.com/WP-API/WP-API, I learned a lot reading the wp-api source
The plugin is copyright Per Soderlind - email@example.com
GPL, please feel free to modify the plugin as long as you make it GPL