update readme

Author: Pslice

README.md

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+# OmegaHH42
+
+A desktop application for monitoring temperature readings from the Omega HH42 thermocouple thermometer.
+
+![License](https://img.shields.io/badge/license-MIT-blue.svg)
+
+## Features
+
+- **Real-time temperature display** - View live readings from your HH42 device
+- **Temperature charting** - Visualize temperature trends over time
+- **Data logging** - Automatically records readings to a local database
+- **CSV export** - Export your data for analysis in Excel or other tools
+- **Cross-platform** - Runs on Windows, macOS, and Linux
+
+## Download
+
+Download the latest release for your platform from the [Releases](https://github.com/Pslice/omega-hh42/releases) page:
+
+| Platform | File |
+|----------|------|
+| Windows | `OmegaHH42 Setup x.x.x.exe` |
+| macOS | `OmegaHH42-x.x.x.dmg` |
+| Linux | `OmegaHH42-x.x.x.tar.gz` |
+
+## Quick Start
+
+1. Connect your Omega HH42 device via USB
+2. Launch OmegaHH42
+3. Select your device's COM port from the dropdown or use Simulate mode
+4. Temperature readings will appear automatically
+
+## Requirements
+
+- Omega HH42 thermocouple thermometer
+- USB cable for device connection
+- Windows 10+, macOS 10.13+, or Linux
+
+## macOS Security Note
+
+Since the app is not signed with an Apple Developer certificate, you may need to right-click the app and select **Open**, then click **Open** in the security dialog.
+
+## Building from Source
+
+```bash
+# Clone the repository
+git clone https://github.com/Pslice/omega-hh42.git
+cd omega-hh42
+
+# Install dependencies
+npm install
+
+# Run in development mode
+npm start
+
+# Build for your platform
+npm run dist:win    # Windows
+npm run dist:mac    # macOS
+npm run dist:linux  # Linux
+```
+
+## Getting Help
+
+If you encounter issues or have questions, please [open an issue](https://github.com/Pslice/omega-hh42/issues) on GitHub.
+
+## License
+
+MIT