feat: extract attachments

[alexfriesen]

What?

Adds the ability to extract attachments.

Why?

This is very useful if you need to process pdf attachments like e-invoices.

How?

It will collect all the attachment data and return an object:

{ 
        name: string
        description: string
        mimeType: string
        data: Buffer
}

Testing?

tests are added.

New Dependencies?

No

Screenshots

Suggested Reading?

Anything Else?

This code is used in my project: https://github.com/alexfriesen/pdf-tools/

Checklist

• I read CONTRIBUTING.md.
• I read MAINTAINERSHIP.md#pull-requests.
• I added/updated unit tests for my changes.
• I added/updated integration tests for my changes.
• I ran the integration tests.
• I tested my changes in Node, Deno, and the browser.
• I viewed documents produced with my changes in Adobe Acrobat, Foxit Reader, Firefox, and Chrome.
• I added/updated doc comments for any new/modified public APIs.
• My changes work for both new and existing PDF files.
• I ran the linter on my changes.