Produce Facture-x/ZUGFeRD invoices | Port reference from upstream repo

This is neither a feature report / nor bug request.

## Goal
Use react-pdf to issue electronic invoices (Facture-x / ZUGFeRD). This requires attaching XML data, adding some XMP markup and a valid PDF/A3 pdf.

## Contribute back / my issue
To implement this I forked this repo and I would like to contribute back, as a lot of changes involve #2613.

Basically I ported the the new reference class from the upstream pdfkit repo.

This works fine except one issue: When adding custom fonts, they look like this (there should be one word "Lorem"):


@diegomura Do you have any idea what might be happening here? The issue must be somewhere at the intersection between the upstream repo's new reference class and how custom fonts are embedded. Maybe there is some overlap with PR in #2696 by @klimeryk

## Further implementation
Once the issue can be resolved and all tests run, I can split work into several more granular PRs. I have a prototype with these features implemented.

- [ ] Port reference and PDF/A compliance from pdfkit. Might be beneficial for long-term goal to use upstream repo again.
- [ ] Allow file attachments
- [ ] XML component to add XML metadata
- [ ] Fixed for the pdfkit lib to actually produce valid PDF/A3 (this is a PR I would also open against upstream, as they have a small spec derivation when attaching files)