Support multilingual embedding models

## Feature Request

Current default model (BGE-small-en-v1.5) is English-optimized. Add support for:

- `BAAI/bge-small-zh-v1.5` (Chinese)
- `intfloat/multilingual-e5-small` (100+ languages)

```python
eg = EmbGrep(model="intfloat/multilingual-e5-small")
```

### Motivation
Non-English codebases and documentation.