Add built-in template for Astro Tailwind

What does this MR do and why?

Contributes to #423450 (closed)

Based on the guidance from https://docs.gitlab.com/ee/development/project_templates.html#adding-a-new-built-in-project-template

How to set up and validate locally

1. Go to create new project page
2. Choose "Create from template" option
3. Select Astro Tailwind template
4. After project creation you should see a Astro Tailwind copy in your GDK

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.