€ sign is dropped

```python
Python 3.13.5 (main, Jun 25 2025, 18:55:22) [GCC 14.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import cutlet
>>> k = cutlet.Cutlet()
>>> k.romaji('€20')
'20'
```
Doesn't happen with $ and ¥ for example. Where € is isn't relevant.