Add app icons for homescreens

[jay-hankins]

Is your feature request related to a problem? Please describe.
Not a problem.

Describe the solution you'd like
I would like a Home Screen icon for iOS.

Describe alternatives you've considered
Pinning the icon to the homescreen leaves a screenshot icon, which isn't desired.

Additional context
Android, iOS, Windows, (& browsers) all have specific directives for app icons. We should add all. There's an easy library on GitHub that can do this.

Best case, we add them into the webpack or build configs; worst case, we do it manually.