docs: create README.md

Author: OleksandrZadvornyi

README.md

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+# ⚡️ Frontend Performance Analyzer
+
+**A simple CLI tool to analyze frontend performance using Lighthouse and Puppeteer.**
+
+- 🧠 Built for developers who care about performance
+- 🚀 Powered by headless Chrome and real metrics
+- 📦 Publish-ready for NPM usage
+
+## 📦 Installation
+
+You can run it instantly via `npx`:
+
+```bash
+npx frontend-performance-analyzer --url https://example.com
+```
+
+Or install it globally:
+
+```bash
+npm install -g frontend-performance-analyzer
+```
+
+## 🚀 Usage
+
+### Analyze a Single URL
+
+```bash
+frontend-performance-analyzer --url https://example.com
+```
+
+### Analyze Multiple URLs
+
+```bash
+frontend-performance-analyzer --url https://example.com https://github.com
+```
+
+### Load URLs from File
+
+```bash
+frontend-performance-analyzer --input urls.txt
+# or
+frontend-performance-analyzer --input urls.json
+```
+
+### Export Report
+
+```bash
+# Save HTML report
+frontend-performance-analyzer --url https://example.com --output report.html
+
+# Save Markdown summary
+frontend-performance-analyzer --url https://example.com --markdown report.md
+
+# Output raw JSON
+frontend-performance-analyzer --url https://example.com --json
+```
+
+### Use Performance Threshold
+
+Exit with failure if score is too low:
+
+```bash
+frontend-performance-analyzer --url https://example.com --threshold 85
+```
+
+## 📊 Sample Output
+
+```
+📊 Performance Metrics for https://example.com
+Score: 93/100
+
+First Contentful Paint: 1.2 s
+Speed Index: 1.9 s
+Largest Contentful Paint: 1.4 s
+Time to Interactive: 1.6 s
+Total Blocking Time: 30 ms
+Cumulative Layout Shift: 0.01
+```
+
+## 📁 Input File Formats
+
+- `.txt`: List of URLs separated by new lines
+- `.json`: JSON array of URLs, e.g. `["https://example.com", "https://github.com"]`
+
+## 🛠 Development
+
+Clone the repo and run:
+
+```bash
+npm install
+node cli.js --url https://example.com
+```
+
+## 📄 License
+
+MIT © 2025 Oleksandr Zadvornyi