Update main README with dual-audience approach #376
Description
Update root README.md to serve both 3D printer owners and developers.
Tasks:
- PRIMARY SECTION: Clear path for 3D printer owners
- "I just want firmware" quick start
- Download links and basic flashing instructions
- Hardware compatibility checker
- Common troubleshooting (friendly language)
- SECONDARY SECTION: Developer and contributor information
- Link to detailed build documentation
- Repository structure explanation
- Contribution guidelines
- TERTIARY SECTION: Repository organization (for reference)
Acceptance Criteria:
- README serves both user types effectively
- All links work correctly
- New users can follow setup instructions
- Professional appearance maintained
Dependencies: Move documentation files
Estimate: 4 story points