Shadcn startup guide needs to be updated

[SteffanEnnis]

By default Tailwind will not scan the components exported as part of the @rjsf/shadcn theme using Vite

This can lead to confusion when migrating off other themes, especially for those who are new to Tailwind

The documenation should link to Tailwinds detecting source files documentation https://tailwindcss.com/docs/detecting-classes-in-source-files and have a line about including the src for a minimal setup

index.css

...
@source "../node_modules/@rjsf/shadcn/src";
....

[tuanphung2308]

I added it in my repo as installation guide for Tailwind v4 last month but forgot to PR into the main repo. I will create a PR later to update the README file