Commit Message:

Enhance Crawl4AI with CLI and documentation updates
  - Implemented Command-Line Interface (CLI) in `crawl4ai/cli.py`
  - Added chunking strategies and their documentation in `llm.txt`

docs/llm.txt/1_introduction.xs.md

@@ -0,0 +1,112 @@
+# Crawl4AI LLM Reference
+
+> Minimal, code-focused reference for LLM-based retrieval and answer generation.
+
+Intended usage: A language model trained on this document can provide quick answers to developers integrating Crawl4AI.
+
+## Installation
+
+- Basic:
+```bash
+pip install crawl4ai
+crawl4ai-setup
+```
+
+- If necessary:
+```bash
+playwright install chromium
+```
+
+## Basic Usage
+
+- Asynchronous crawl:
+```python
+import asyncio
+from crawl4ai import AsyncWebCrawler
+
+async def main():
+    async with AsyncWebCrawler(verbose=True) as c:
+        r = await c.arun(url="https://example.com")
+        print(r.markdown)
+
+asyncio.run(main())
+```
+
+## Concurrent Crawling
+
+- Multiple URLs:
+```python
+urls = ["https://example.com/page1", "https://example.com/page2"]
+async with AsyncWebCrawler() as c:
+    results = await asyncio.gather(*[c.arun(url=u) for u in urls])
+```
+
+## Configuration
+
+- CacheMode:
+```python
+from crawl4ai import CacheMode
+r = await c.arun(url="...", cache_mode=CacheMode.ENABLED)
+```
+
+- Proxies:
+```python
+async with AsyncWebCrawler(proxies={"http": "http://user:pass@proxy:port"}) as c:
+    r = await c.arun("https://example.com")
+```
+
+- Headers & Viewport:
+```python
+async with AsyncWebCrawler(headers={"User-Agent": "MyUA"}, viewport={"width":1024,"height":768}) as c:
+    r = await c.arun("https://example.com")
+```
+
+## JavaScript Injection
+
+- Custom JS:
+```python
+js_code = ["""
+(async () => {
+    const btn = document.querySelector('#load-more');
+    if (btn) btn.click();
+    await new Promise(r => setTimeout(r, 1000));
+})();
+"""]
+
+r = await c.arun(url="...", js_code=js_code)
+```
+
+## Extraction Strategies
+
+- JSON CSS Extraction:
+```python
+from crawl4ai.extraction_strategy import JsonCssExtractionStrategy
+
+schema = {...}
+r = await c.arun(url="...", extraction_strategy=JsonCssExtractionStrategy(schema))
+```
+
+- LLM Extraction:
+```python
+from crawl4ai.extraction_strategy import LLMExtractionStrategy
+
+r = await c.arun(url="...",
+    extraction_strategy=LLMExtractionStrategy(
+        provider="openai/gpt-4o",
+        api_token="YOUR_API_KEY",
+        schema={...},
+        extraction_type="schema"
+    )
+)
+```
+
+## Common Issues
+
+- Playwright errors: `playwright install chromium`
+- Empty output: Increase wait or use `js_code`.
+- SSL issues: Check certificates or use `verify_ssl=False` (not recommended for production).
+
+## Additional Links
+
+- [GitHub Repository](https://github.com/unclecode/crawl4ai)
+- [Documentation](https://crawl4ai.com/mkdocs/)