More details for configuring Ollama (#252)

There didn't appear to be any existing docs on what `ollama_api_base`
should look like.

## What this does

Updates docs/configuration.md to make it clearer how to configure use
with ollama

## Type of change

- [ ] Bug fix
- [ ] New feature
- [ ] Breaking change
- [x] Documentation
- [ ] Performance improvement

## Scope check

- [x] I read the [Contributing
Guide](https://github.com/crmne/ruby_llm/blob/main/CONTRIBUTING.md)
- [x] This aligns with RubyLLM's focus on **LLM communication**
- [x] This isn't application-specific logic that belongs in user code
- [x] This benefits most users, not just my specific use case

## Quality check

- [n/a] I ran `overcommit --install` and all hooks pass
- [x] I tested my changes thoroughly
- [x] I updated documentation if needed
- [x] I didn't modify auto-generated files manually (`models.json`,
`aliases.json`)

## API changes

- [ ] Breaking change
- [ ] New public methods/classes
- [ ] Changed method signatures
- [x] No API changes

## Related issues

<!-- Link issues: "Fixes #123" or "Related to #123" -->

---------

Co-authored-by: Carmine Paolino <carmine@paolino.me>

Author: jslag

docs/configuration.md

@@ -105,9 +105,13 @@ Set the corresponding `*_api_key` attribute for each provider you want to enable
 *   `gemini_api_key`
 *   `deepseek_api_key`
 *   `openrouter_api_key`
-*   `ollama_api_base`
 *   `bedrock_api_key`, `bedrock_secret_key`, `bedrock_region`, `bedrock_session_token` (See AWS documentation for standard credential methods if not set explicitly).
 
+## Ollama API Base (`ollama_api_base`)
+
+When using a local model running via Ollama, set the `ollama_api_base` to the URL of your Ollama server, e.g. `http://localhost:11434/v1`
+
+
 ## Custom OpenAI API Base (`openai_api_base`)
 {: .d-inline-block }