Release v2.5.6

What's Changed

• Update README.md by @suji-cho in #2
• docs: Update project name to OpenDataLoader PDF by @hyunhee-jo in #3
• Update README.md by @suji-cho in #4
• refactor: Implement monorepo structure and refactor Java project by @hyunhee-jo in #5
• fix: Standardize line endings and update binary file patterns by @hyunhee-jo in #6
• build: Refine Python build system and improve CI/CD environment by @hyunhee-jo in #7
• chore(license): [OSS Spread] Reflect legal review #45 by @hyunhee-jo in #8
• Add log for filtering zero height text by @LonelyMidoriya in #702
• feat(tagging): keep background vectors, order /ParentTree, and give captions their own level by @bundolee in #713

Full Changelog: https://github.com/opendataloader-project/opendataloader-pdf/commits/v2.5.6