Hey Siddarth
Hashnode's editor is built in-house. But you can totally build something like this using Draft. Here is a resource that was written by @saiki a couple of years back, but it might be relevant - github.com/fatman-/learn-draftjs
Also, check learn-draftjs.now.sh and hashnode.com/post/about-draftjs-cjc1xck4m056rfnwt…
Let us know if you have more questions!