Unsure what values to use for "fonts" in -product-icon-theme.json

Refs: #93798

What should `style`, `weight`, and `size` be set to? Should they be unset unless they are specifically needed? What would `size` even do? Isn't the size based on the usage? Also, should there be intellisense for `style` and `weight`?

For `src`, what formats do we support? Should there be intellisense for them?

