jbig2 doc: mention pkg-config #673

Job	Run time
Test Windows (windows-latest, 3.12)	6m 48s
Test Windows (windows-latest, 3.10)	6m 56s
Test Windows (windows-latest, 3.11)	6m 57s
Build sdist and wheels	18s
Test macOS (macos-latest, 3.10)	4m 44s
Test macOS (macos-latest, 3.13)	4m 21s
Test macOS (macos-latest, 3.11)	4m 55s
Test Windows (windows-latest, 3.13)	6m 40s
Test macOS (macos-13, 3.10)	7m 37s
Test macOS (macos-13, 3.11)	8m 5s
Test macOS (macos-13, 3.12)	8m 24s
Test macOS (macos-latest, 3.12)	4m 45s
Test macOS (macos-13, 3.13)	8m 29s
Test ubuntu-22.04 with Python 3.11	5m 9s
Test ubuntu-24.04 with Python 3.12	5m 31s
Test ubuntu-22.04 with Python 3.12	6m 37s
Test ubuntu-24.04 with Python 3.10	5m 28s
Test ubuntu-24.04 with Python 3.11	5m 54s
Test ubuntu-22.04 with Python 3.13	5m 8s
Test ubuntu-22.04 with Python 3.10	5m 36s
Test ubuntu-24.04 with Python pypy3.10	10m 6s
Test ubuntu-24.04 with Python 3.13	5m 29s
Build Ubuntu-based Docker image	32m 1s
Build Alpine-based Docker images	2m 43s
Deploy artifacts to PyPI	0s
Create GitHub release	-1s
	2h 48m 40s

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