Adding Tailwind v4 to Docusaurus v3

This guide explains how to set up Tailwind CSS v4 with Docusaurus v3. It involves installing necessary packages (tailwindcss, postcss, @tailwindcss/postcss) and creating a custom Docusaurus plugin to integrate Tailwind. The plugin configures PostCSS to use Tailwind and is added to the Docusaurus configuration. Finally, importing Tailwind in a custom CSS file enables its use and custom dark mode variant.