name : full name, appears on splash screen
short_name : short name for use on tabs and places with short spaces
start_url : when you CLICK on the app, which page gets served first? (might not need to be the main page)
scope : which parts of this app is PWA? (you can wall of your PWA-ness to a small part of the app, or everything)
display : standalone (looks like a standalone app, no browser url bar and everything)
background_color : colour when the app is loading and on splashscreen
theme_color : toolbar color esp on the task switcher
description : used rarely for now (in favourites, or popups)
dir : direction, NOT directory! specifies reading direction. hmm.
lang : main language (useful for browser, maybe for translation purposes?)
orientation : preferred or enforced default orientation
icons : a set of icons that the os will pick for best-fit size for use in homescreen or tabs or stuff
related_applications : other versions of the app you wanna provide to the user as a choice of installation (like play store app, or windows store app)