Allow setting read_timeout

When using Gemini 2.5 pro I usually get read timeouts:

```
Conn close because of error Net::ReadTimeout
```

Would love an option to set the http's read_timeout parameter:
https://ruby-doc.org/stdlib-2.6.3/libdoc/net/http/rdoc/Net/HTTP.html#method-i-read_timeout-3D

