JavaScript for chat iFrame

We need to create a JS file that clients can install to run our chat application within an iFrame on their website. This requires some special use of cookies and specific JS experience with generating iFrames for a different domain than the parent page. If you have created something similar, we'd like to engage you to help with this project. Your role will be to provide guidance to one of our developers and write the specific JS for that purpose. Our product is a Vue.js 3 application, so please have experience with that framework.