Update the Tailwind CSS setup guide

[diepoe]

I updated the tailwindcss guide to work with version 3; I also updated that the config file should be created with the tailwind cli.

[vercel[bot]]

This pull request is being automatically deployed with Vercel (learn more).
To see the status of your deployment, click below or on the icon next to each commit.

🔍 Inspect: https://vercel.com/roxi/routify-dev/6efGN4PAtnujjK7343ywxMXJPeDo
✅ Preview: https://routify-dev-git-fork-haudraufhaun-update-guide-tailwind-roxi.vercel.app