This looks like an OCaml.org build. It is currently being documented, but the recommended way for building the ocaml.org site on a Windows machine right now is using WSL. See the related issues:
- Error while setting up ocaml project using WSL
- Improve the Success Stories page · Issue #1258 · ocaml/ocaml.org · GitHub
There are a lot of scripts and Makefiles so it seems this is the quickest way to contribute is to use WSL. It also seems @YASHI_VIJAY has already managed to build the site this way so it is a little more tried and tested :))