Hi Ayush!
I have some experiences to write language frontend on Guile.
Here are posts and project you can take a look, they could be helpful to you.
I actually have a very preliminary project to implement ES10, however, I never have time to finish it since I started my own company.
ES10 has small fixes compared with ES6, so it's mostly ES10. Anyway, _javascript_ is a big language to implement.
I'm still interested in _javascript_ frontend. I can answer questions as I can if you really want to make your hands dirty.
Best regards.