Add a README.md that gives developers a quick understanding of what
Aether is and how to get started. Includes:
- Project description and why Aether exists
- Installation instructions
- Quick start code example showing event creation, persistence, and replay
- Key concepts (immutability, derived state, version consistency)
- Links to further documentation
- CI badge
Closes#44
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
