Add support for es6 import specifier details

[Riley19280]

Currently, given an import such as import { Foo, Bar } from './utilities', the returned dependencies will only give ['utilities'], and no other details about what specifically was imported.

For example, the previous import in the page.ts file:

// Directory Structure
├── page.ts
└── utilities
    ├── index.ts
    ├── foo.ts
    ├── bar.ts
    └── baz.ts

// utilities/index.ts
export * from './foo'
export * from './bar'
export * from './baz'

These details would be incredibly useful in other places such as dependency-tree so that the specific imports could be traced.

Currently when getting the dependencies for page.ts it would be utilities/index.ts, and utilities/index.ts would depend on foo, bar, and baz. This gives the appearance that page.ts depends on foo, bar, and baz, even though it only imports Foo and Bar.

I would be happy to PR this improvement to this package if this is an acceptable addition. When implementing it, I would add an opt-in config option to retrieve the extra import declaration data, and then pass it to the onAfterFile callback for use in other locations.