docs: add pixelshot CLI usage examples (#62)

* docs: add pixelshot CLI usage examples to README

* docs: use real tested URLs in pixelshot CLI examples

* docs: move CLI examples below programmatic section

Author: yichuan-w

README.md

@@ -214,6 +214,20 @@ from pixelrag_render import render_url
 tiles = render_url("https://en.wikipedia.org/wiki/Python", "./tiles")
 ```
 
+The same rendering is available as a CLI — `pixelshot` ships with `pip install pixelrag`:
+
+```bash
+# Web page → tiles (headless Chromium via CDP)
+pixelshot https://en.wikipedia.org/wiki/Python -o ./tiles
+
+# PDF → tiles (requires poppler; install the pdf extra: pip install 'pixelrag[pdf]')
+curl -sL -o paper.pdf https://arxiv.org/pdf/2503.09516
+pixelshot paper.pdf -o ./tiles --dpi 200
+
+# URLs and local files can be mixed freely
+pixelshot https://github.com/StarTrail-org/PixelRAG paper.pdf -o ./tiles
+```
+
 ### Embed tools (standalone)
 
 Each stage runs independently, without the orchestrator: