PDFx test for sample-newsletter.pdf

Input: sample-newsletter.pdf

(cd "sample-newsletter.pdf_dir" && uv run --project "$repo_root" pdfx -t "sample-newsletter.pdf_name" -o "sample-newsletter--pdfx-python.txt")

(cd "sample-newsletter.pdf_dir" && uv run --project "$repo_root" pdfx -j "sample-newsletter.pdf_name" -o "sample-newsletter--pdfx-python.json")