Setup some files to make package ready for v0.0.1

[gustavoguichard]

Purpose

This PR contains:

• Little refactoring to split files and tests into subjects
• Commands to build the package and make it ready to publish / test locally
• Prettier config
• Vitest setup to polyfill req/res in node env
• Some fixes I had to change after testing locally

I consider this PR contains the minimum to release our first version 🥳