Editing Google App Script manifesto to add to home screen?

I have been following this codelab to fit my purpose of adding a Google App Script html service page to home-screen on a mobile device:

https://codelabs.developers.google.com/codelabs/add-to-home-screen/#1

However I am not creating a Web Server for Chrome, is it possible to achieve this with the html service?

At the moment of editing the manifesto and republishing as web app it reverts any changes done to it. I have attempted to host my json manifesto on external sites and DevTools still cannot detect it.

My index.html from App Script.











Some HTML..

My Google App Script Web App is fully functional and can be accessed through a the /exec link, I want to implement it to mobile home-screen but I don’t know if the manifesto is truly being edited as upon publishing it reverts any changes done to it.