v0.8

What's Changed

• Fixed ModuleNotFoundError: No module named 'column_data' (#29) — switched to relative imports
• Fixed misleading error on PDF parse failures like PNG filter 4 (#9) — now raises clear FileNotFoundError or ValueError with the actual cause
• Fixed extended_columns() mutating global state on repeated calls
• Expanded test suite from 3 to 78 tests across all 3 test PDFs
• Added GitHub Actions workflow for automated PyPI publishing on release