Fix: Directly export Named type to avoid ambiguity with TS --isolatedModules option

[Tenga]

Description of changes:

We've recently attempted to update from 3.0.0-rc9 to 3.0.0 and encountered the following issue when using style-dictionary within our project that uses --isolatedModules via config (Next.js project, Next.js uses Babel to compile):

./node_modules/style-dictionary/types/_helpers.ts:16:10
Type error: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

  14 | type Named<T> = T & { name: string; };
  15 |
> 16 | export { Named }

This PR makes the change of exporting the type directly inline to avoid this issue, as you are already using that syntax within styled-dictionary.

I believe the alternative means of fixing this are:

• Having this file be a .d.ts file - Didn't want to mess with file names
• Using export type { Named } - TS 3.8+

If necessary, context around --isolatedModules by the TS authors around this specific issue.

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[chazzmoney]

Thanks for your contribution!

LGTM