Incorrect default value for type definitions file path listed in docs

[joepaolicelli]

The docs say the default is for the types directory to be in the rootDir, while it is actually expected to be in the sourceDir. While these are often the same in Nuxt v3 they don't have to be, and they will be different in Nuxt v4. (A starter repo from NuxtHub already makes them different, which is why I ran into this.)

https://github.com/nuxt-modules/supabase/blob/be41d946bc6dabe75c7f92d0494f8d86738c0864/docs/content/2.get-started.md?plain=1#L141

https://github.com/nuxt-modules/supabase/blob/be41d946bc6dabe75c7f92d0494f8d86738c0864/src/module.ts#L98

Apologies for creating an issue for a one character documentation change! But this caused me some confusion and brief issues, and seemed like a simple fix. I'm happy to make a PR, but wasn't sure if that would be more work for you than just a note.