docs: Add release notes for v3.1.8

- Comprehensive release notes with bug fixes and improvements
- Migration guide and example usage
- Technical details for developers

Author: TexasCoding

RELEASE_NOTES_3.1.8.md

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+# Release v3.1.8 - Real-time Data Reliability Improvements
+
+## 🎯 Overview
+This release addresses critical issues with real-time data processing for futures contracts, particularly improving support for E-mini futures (NQ, ES) and ensuring consistent bar generation during low-volume trading periods.
+
+## 🐛 Bug Fixes
+
+### Fixed Symbol Resolution for E-mini Futures
+- **Issue**: E-mini futures like NQ (which resolves to ENQ) and ES (which resolves to EP) were not receiving real-time updates
+- **Root Cause**: Symbol matching logic only checked the original instrument name, not the resolved symbol ID
+- **Solution**: Enhanced symbol validation to check both the user-specified instrument and the resolved symbol ID
+- **Impact**: All futures contracts now work correctly with real-time data feeds
+
+### Fixed Bar Generation During Low-Volume Periods
+- **Issue**: OHLCV bars were only created when new ticks arrived, causing gaps during low-volume periods
+- **Root Cause**: No periodic bar creation mechanism for quiet market periods
+- **Solution**: Implemented a bar timer task that creates empty bars at proper intervals even without trading activity
+- **Impact**: Consistent bar generation across all timeframes regardless of trading volume
+
+## 🔧 Technical Improvements
+
+### Enhanced Error Handling
+- Added robust error handling for bar time calculations
+- Improved error recovery in bar timer loop to prevent task termination
+- Better logging for debugging symbol resolution issues
+
+### Code Quality Improvements
+- Fixed asyncio task warnings by properly storing task references
+- Improved unit conversion clarity with explicit mapping dictionary
+- Optimized DataFrame operations for better performance
+
+## 📊 Affected Components
+- `RealtimeDataManager` - Core real-time data processing
+- Symbol validation and matching logic
+- Bar creation and timing mechanisms
+- Event emission system
+
+## 🚀 Migration Guide
+No breaking changes. This version is fully backward compatible with v3.1.x.
+
+Simply update to v3.1.8 to benefit from improved real-time data reliability:
+```bash
+pip install --upgrade project-x-py==3.1.8
+```
+
+## 📝 Example Usage
+```python
+from project_x_py import TradingSuite
+
+# Works with all futures contracts now
+suite = await TradingSuite.create(
+    instrument="NQ",  # E-mini Nasdaq now works correctly
+    timeframes=["1min", "5min"],
+    initial_days=1
+)
+
+# Bars will be created consistently even during low-volume periods
+# No gaps in your data during quiet market times
+```
+
+## 🎉 Benefits
+- **Improved Reliability**: All futures contracts now receive real-time updates correctly
+- **Consistent Data**: No more gaps in bar data during low-volume periods
+- **Better Trading**: More reliable data for trading strategies, especially for E-mini futures
+- **Zero Breaking Changes**: Drop-in replacement for v3.1.7
+
+## 🙏 Acknowledgments
+Special thanks to our users for reporting these issues and helping us improve the real-time data system.
+
+## 📚 Documentation
+For more details, see:
+- [CHANGELOG.md](./CHANGELOG.md) - Complete change history
+- [Real-time Data Manager Documentation](./docs/realtime_data_manager.md)
+- [Example Scripts](./examples/realtime_data_manager/)
+
+---
+*Released: January 2025*
+*Version: 3.1.8*
+*Status: Production Ready*