A function that waits for a specific element to load before running a specified callback. portated from this GitHub gist: https://gist.github.com/BrockA/2625891#file-waitforkeyelements-js
Dette script bør ikke installeres direkte. Det er et bibliotek, som andre scripts kan inkludere med metadirektivet // @require https://update.greasyfork.org/scripts/476008/1255570/waitForKeyElements%20gist%20port.js
