fix(theme): use @theme inline to properly reference css variables

Resolves #4018

https://tailwindcss.com/docs/theme#referencing-other-variables

Author: benjamincanac

src/templates.ts

@@ -77,7 +77,7 @@ export function getTemplates(options: ModuleOptions, uiConfig: Record<string, an
     write: true,
     getContents: () => `@source "./ui";
 
-@theme default {
+@theme default inline {
   --color-old-neutral-50: ${colors.neutral[50]};
   --color-old-neutral-100: ${colors.neutral[100]};
   --color-old-neutral-200: ${colors.neutral[200]};