Execute and point to a folder using arg -path=c:\haicons\ and it will generate a custom-icons.js that you can use as a resource in home assistant.
I wanted custom icons, came across this thread https://community.home-assistant.io/t/lovelace-collasping-ps4-controller-card-with-icons/198040
There was no way I was going to create a custom-icons.js by hand, and then maintain it.