Atomizer + PDF extractor

[joepio]

At this moment highly WIP.

Todo:

• Wait for PR in pdf-extractor to be merged.
• Consider other import libraries like https://crates.io/crates/pdfium-render
• Create Classes and Properties for Files (e.g. ImageFile and PDFFile)

PR Checklist:

• Link to related issues: Atomizer - recognize file types and convert to JSON-AD #434
• Add changelog entry linking to issue, describe API changes
• Add tests (optional)
• (If new feature) add to description / readme

[joepio]

Saw this library which may support PDF text extraction?

[joepio]

Relevant: #477