Ternary contour plot

Hello everyone !

For a project I have, I’m trying to do a ternary contour plot with Plotly.js.
The only resource I’ve found so far is from the official website : Ternary Contour Plots | JavaScript | Plotly
The issue is, I’m trying to do a ternary diagram with the isovalue lines like this :

Even with trials and the documentation I linked, I’m at loss.

Every other resources I’ve found was using Plotly.py. If anyone has something that could help me, it would be very welcomed.