Provide UI or script to change PWA icon for mobile home screen

[eyand]

Is your proposal related to a problem?

When using "add to home screen" in mobile Firefox on Android, the icon that appears is the default Lemmy icon rather than my custom icon that appears elsewhere in the app.

Describe the solution you'd like

There are a few approaches to resolving this, in my view:

• Provide documentation to instance admins on how to change this manually. It's a one-time change, so it's probably fine to do it the hard way.
• Add UI to upload the icon scaled to different sizes
• Backend code to automatically rescale the uploaded site icon to whatever sizes are needed for use on the mobile home screen.