Add PyPI installation documentation

- Created PYPI_INSTALLATION.md with detailed installation and usage instructions
- Updated README.md to feature uvx/pip installation as recommended method
- Updated README_EN.md with same changes for English documentation

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

README_EN.md

@@ -25,6 +25,25 @@ LangBot is an open-source LLM native instant messaging robot development platfor
 
 ## 📦 Getting Started
 
+#### Quick Start (Recommended)
+
+Use `uvx` to start with one command (no installation required):
+
+```bash
+uvx langbot
+```
+
+Or install with `pip` and run:
+
+```bash
+pip install langbot
+langbot
+```
+
+Visit http://localhost:5300 to start using it.
+
+Detailed documentation [PyPI Installation](docs/PYPI_INSTALLATION.md).
+
 #### Docker Compose Deployment
 
 ```bash