What is the easiest way to implement WYSWYG in react that can support formatting as what we have here on stackoverflow that we can easily format code blocks or even better as what we can see on medium site?
You can try Draft.js
Draft.js is a framework for building rich text editors in React, powered by an immutable model and abstracting over cross-browser differences.
Draft.js makes it easy to build any type of rich text input, whether you're just looking to support a few inline text styles or building a complex text editor for composing long-form articles.