[new package] Powerset barrel exports for Astro

[Fryuni]

Barrel files in Astro cause the styles and scripts from all the re-exported components to be included in any page that uses any one of them.

// src/components/index.ts
export Foo from './Foo.astro';
export Bar from './Bar.astro';

Then on a page:

// src/pages/index.astro
---
import {Foo} from '../components';
---
<Foo/>

That index page will include the styles and client-side scripts from the Bar component.

---

While this is not fixed in Astro core, it could be provided as a virtual import that dynamically (and lazily) expands into the powerset of possible imports.

For the example above:

• import {Foo} from '~anyComponent'; would resolve to a module containing:

  export Foo from '/src/components/Foo.astro';

• import {Bar} from '~anyComponent'; would resolve to a module containing:

  export Bar from '/src/components/Bar.astro';

• import {Foo, Bar} from '~anyComponent'; would resolve to a module containing:

  export Bar from '/src/components/Bar.astro';
  export Foo from '/src/components/Bar.astro';