feat: update packages and overhaul onboarding
What
- Upgrade astro & related components to newer versions
- Overhaul Runway onboarding guide
Why
I got carried away with the astro & starlight documentation to improve the onboarding doc and this is the result.
Note to reviewer: it's hard to look at the diff of changes due to the number of line changes so the easiest way is to run npm run dev
locally and look at the onboarding guide yourself.