Detect any new DOM Element by its CSS Selector, then trigger a function. Includes Promise- & Callback interface. Based on ES6 MutationObserver. Ships legacy waitForKeyElements interface, too.
This script should not be not be installed directly. It is a library for other scripts to include with the meta directive // @require https://update.greasyfork.org/scripts/374849/1060689/Library%20%7C%20onElementReady%20ES7.js