Explain how to re-build esprima-bin-wrapper

[tinchodias]

Pharo code invokes a node js file that's the webpack output.

Invoked js file: esprima-bin-wrapper/dist/esprima-bin-wrapper.node.js
Invocation: src/Hunter-AST.package/HNEsprimaWrapper.class/class/esprimaWrapperPathRelativeTo..st

I propose to explain this in root's README or in the one of this subdirectory: https://github.com/dorellang/hunter/blob/master/esprima-bin-wrapper/README.md

---

Motivation: there are pending updates to dependencies (for example, 5 PR generated by "dependabot"). I didn't update yet because, in part, they don't seem to be really a problem, but also because I didn't know how to re-build the js that's invoked by the code. Today I realized it was not difficult at all, but I think it's better to explain it in README.