docs: Add comprehensive documentation and examples

This commit significantly improves project documentation with comprehensive
guides, examples, and references to help users and contributors.

New Documentation Files:

1. CONTRIBUTING.md (280 lines)
   - Development setup instructions
   - Coding standards and style guidelines
   - Testing requirements
   - Commit message conventions
   - Pull request process
   - Debugging and profiling tips

2. ARCHITECTURE.md (450 lines)
   - System architecture overview with diagrams
   - Component descriptions (Manager, Protocol, TLS/DTLS, Network)
   - Data flow diagrams (journal to network)
   - Connection state machine
   - Protocol format specifications (RFC 5424/3339/5425)
   - Security model and privilege dropping
   - Performance considerations
   - Future enhancement ideas

3. TESTING.md (550 lines)
   - Unit test guide with cmocka
   - Integration testing with local syslog servers
   - TLS/DTLS testing with certificate generation
   - Manual testing scenarios
   - Protocol compliance validation
   - Security testing procedures
   - Performance testing methodology
   - CI pipeline documentation

4. FAQ.md (400 lines)
   - General questions about the project
   - Installation and setup help
   - Configuration examples and explanations
   - Network protocol selection guide
   - Log format differences
   - Troubleshooting common issues
   - Security best practices
   - Performance optimization tips
   - Cloud service integration

Examples Directory (10 configuration files):

- examples/README.md - Overview and usage instructions
- examples/basic-udp.conf - Simple UDP multicast
- examples/basic-tcp.conf - Reliable TCP delivery
- examples/tls-secure.conf - Encrypted TLS with certificates
- examples/dtls-encrypted.conf - DTLS encrypted datagrams
- examples/cloud-papertrail.conf - Papertrail integration
- examples/cloud-loggly.conf - Loggly integration
- examples/filtering.conf - Sensitive log filtering
- examples/structured-data.conf - RFC 5424 structured data
- examples/high-performance.conf - High-volume optimization
- examples/development.conf - Development/testing setup

README.md Improvements:

- Added Documentation section with links to all guides
- Added Configuration Examples section linking to examples/
- Improved Getting Help section with resource links
- Better navigation to specialized documentation

Documentation Statistics:
- Total new documentation: ~1,700 lines
- Example configurations: 10 files
- Comprehensive coverage: Architecture, Testing, Contributing, FAQ
- Ready-to-use examples for common scenarios

Benefits:
- Lower barrier to entry for new contributors
- Better understanding of internal architecture
- Easier troubleshooting with FAQ
- Production-ready configuration examples
- Comprehensive testing guidance

Author: ssahani

ARCHITECTURE.md

@@ -245,12 +245,47 @@ gcc tag.c -lsystemd -o tag && ./tag
 
 ## Contributing
 
-1. Fork it
+We welcome contributions! Please see our comprehensive contribution guide:
+
+📖 **[CONTRIBUTING.md](CONTRIBUTING.md)** - Development setup, coding standards, and PR guidelines
+
+Quick start:
+1. Fork the repository
 2. Create your feature branch
-3. Commit with clear messages
-4. Open a PR!
+3. Add tests for new functionality
+4. Submit a pull request
+
+---
+
+## Documentation
+
+Comprehensive documentation is available:
+
+| Document | Description |
+|----------|-------------|
+| **[README.md](README.md)** | This file - Quick start and configuration guide |
+| **[ARCHITECTURE.md](ARCHITECTURE.md)** | Internal architecture and design decisions |
+| **[CONTRIBUTING.md](CONTRIBUTING.md)** | Development setup and contribution guidelines |
+| **[TESTING.md](TESTING.md)** | Testing guide with examples |
+| **[FAQ.md](FAQ.md)** | Frequently asked questions |
+| **[examples/](examples/)** | Sample configuration files for common scenarios |
 
-See `CONTRIBUTING.md`
+---
+
+## Configuration Examples
+
+See the [examples/](examples/) directory for ready-to-use configurations:
+
+- **[basic-udp.conf](examples/basic-udp.conf)** - Simple UDP multicast
+- **[basic-tcp.conf](examples/basic-tcp.conf)** - Reliable TCP delivery
+- **[tls-secure.conf](examples/tls-secure.conf)** - Encrypted TLS with certificate validation
+- **[dtls-encrypted.conf](examples/dtls-encrypted.conf)** - Encrypted DTLS datagrams
+- **[cloud-papertrail.conf](examples/cloud-papertrail.conf)** - Papertrail cloud service
+- **[cloud-loggly.conf](examples/cloud-loggly.conf)** - Loggly cloud service
+- **[filtering.conf](examples/filtering.conf)** - Filter sensitive logs
+- **[structured-data.conf](examples/structured-data.conf)** - Use structured data
+- **[high-performance.conf](examples/high-performance.conf)** - Optimized for high volume
+- **[development.conf](examples/development.conf)** - Development/testing setup
 
 ---
 
@@ -261,5 +296,11 @@ See `LICENSE`.
 
 ---
 
-> **Questions?** Open an issue on GitHub!
-> **Star this repo if you love centralized logging!**
+## Getting Help
+
+- 📖 **[FAQ](FAQ.md)** - Frequently asked questions
+- 🐛 **[Issues](https://github.com/systemd/systemd-netlogd/issues)** - Report bugs or request features
+- 💬 **[Discussions](https://github.com/systemd/systemd-netlogd/discussions)** - Community Q&A
+- 📚 **[Documentation](ARCHITECTURE.md)** - Deep dive into internals
+
+> **Star this repo if you find it useful!**