docs: add Project Setup section to Developer Guide

Author: 2nofa11

docs/developer-guide/index.md

@@ -2,6 +2,16 @@
 
 Contributing is welcome.
 
+## Project Setup
+
+To develop locally, fork the eslint-plugin-vue repository and clone it in your local machine. The package manager used to install and link dependencies must be [npm](https://www.npmjs.com/). You need to use the LTS version of [Node.js](https://nodejs.org/).
+
+To develop and test the `eslint-plugin-vue` package:
+
+1. Run `npm install` in the project's root folder.
+
+2. Run `npm test` to make sure everything is set up correctly.
+
 ## :bug: Bug reporting
 
 If you think you’ve found a bug in ESLint, please [create a new issue](https://github.com/vuejs/eslint-plugin-vue/issues/new?labels=&template=bug_report.md) or a pull request on GitHub.