It's already built into Apple Maps. Or are you saying that this has not worked for you?

https://support.apple.com/guide/iphone/set-up-electric-vehic...

"A Better Trip Planner" by these guys is pretty good in my experience:

https://www.iternio.com/

The Tesla navigation system has supercharger routing built in.

Won’t be surprise if Google maps has this within 5 years too.