How can you make such live smoke on a css and js site?
You can use sprites, I have no ready-made smoke, but there is a candle for an example:
You can try to make this AfterEffects smoke, there are probably a bunch of tutorials. Then export using bodymovin to json format for lottieweb
You can also try using particles and get it moving.
Actually, here's something similar: https://mrdoob.com/#/144/magic_dustAnonymous
To place the code, please use CodePen or similar tool. Thanks you!