Add GitHub ingestion - pull content from repos as source material

- GitHubIngestor class to fetch repo contents
- Support for .md, .txt, .notes, .draft files
- Method to ingest from GitHub directly into orchestrator
- Export GitHubIngestor in __init__.py

Usage:
    orch = OpusOrchestrator(book_type='fiction', genre='memoir')
    content = await orch.ingest_from_github('mrhavens/my-notes')
    await orch.run()

opus_orchestrator/__init__.py

@@ -28,6 +28,7 @@ from opus_orchestrator.schemas import (
 from opus_orchestrator.state import OpusState, create_initial_state
 from opus_orchestrator.langgraph_workflow import OpusGraph, run_opus, OpusGraphState
 from opus_orchestrator.autogen_critique import CritiqueCrew, create_critique_crew
+from opus_orchestrator.utils.github_ingest import GitHubIngestor, create_github_ingestor
 from opus_orchestrator.frameworks import StoryFramework
 
 __all__ = [