pwa-asset-generator only generates one favicon size, breaking logos with variants for smaller sizes

[dantman]

Is your feature request related to a problem? Please describe.
pwa-asset-generator only generates one large favicon. This is despite the fact that you can specify a html icon that adapts to other sizes.

Not all sizes of icon can work simply by having the browser take the largest raster image and scale it.

• If you have a vector source then going from vector -> 196x196 raster -> scaling to 16x16 could result in an undesirable lost of detail as the browser has to interpolate a raster image instead of just rendering a vector or using a vector that is a multiple of 16x16.
• Tiny icons like the ones in browser tabs can require adjusting or swapping. (non-favicon example)
  • Some parts of a logo may need to be adjusted in size because important details disappear at small sizes.
  • A logo may be completely unintelligible at these small sizes and it may be desirable

That last one is my current case. The logo of my current project is good for the larger site icons, but at the tab size it becomes unintelligible. So our designer designed a variant of the icon that works at tiny sizes.

However, even though I have a html source that switches between the variant at 48px and below, because pwa-asset-generator only generates one favicon the larger logo is squished into the tab instead of the correct variant for tiny icons being used.

Describe the solution you'd like
Ideally there would be a way to specify additional favicon sizes you can use.

Describe alternatives you've considered
I've considered specifying SVG favicons directly for the small sizes. But pwa-asset-generator erases the custom link tags I add to my index.html. And Safari doesn't support colored SVG icons so I still need a PNG/ICO version.