Docs Migration to Starlight notes - for 4.0 blog post

Points re: the migration process:

- BENEFIT: allows us to unify our development: improvements to docs feed into Starlight and vice versa
- BENEFIT: people always asked how to "get docs like Astro's" but some of our custom additions were not available in our old docs template, nor yet in Starlight.
- Early Starlight development was focused on the basics, and what would work for everyone. For example, the first version of Starlight shipped with a built-in search, essential for a docs site, that didn't require you to have an account or API access.
- We've spent this last quarter taking our Docs features (things that Docs did that weren't immediately available in Starlight: special components, code highlighting, tutorial tracker, Algolia widget) and built them in Starlight, and FOR Starlight. For example, the latest version of Starlight includes the option to replace the built-in search and connect to your own Algolia account, like our own Astro Docs does.
- Upgrade or start a new Starlight docs project today to have access to existing Astro Docs features like:
- Expressive Code, the premiere tool for expressing your code on the web
- An Algolia plugin, an enterprise-grade digital search platform
- Several documentation-specific custom components originally built for Astro Docs, with more to come such as an interactive file tree and multiple-choice quiz

Extra things that could be mentioned:

- rachel nabors tweet "you can get it all out of the box with their Starlight project"

Video Transcript:

> “[you can use] Docusaurus or Starlight from Astro. I used to think the React docs or the Stripe docs were the best docs in the world. I now have to say I tip my hat to the Astro team. They’ve got like 800 people working on docs in their community around the clock and they have evolved how docs can be done… and you can get it all out of the box with their Starlight project. So shout out to the Astro team and the Starlight team specifically.”