docs: document OrcaRouter as an OpenAI-compatible service

Add a named OrcaRouter entry in the OpenAI section of the README, mirroring
the existing OpenAI/Ollama examples. SourceGit's AI feature works with any
OpenAI-compatible HTTP API; the new entry shows the exact Server URL, API key
prefix, and a starting model for OrcaRouter.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: putraperdana1207-pixel

README.md

@@ -194,6 +194,12 @@ For `OpenAI`:
 
 * `Server` must be `https://api.openai.com/v1`
 
+For `OrcaRouter`:
+
+* `Server` should be `https://api.orcarouter.ai/v1`
+* `API Key` should be an OrcaRouter API key (prefixed with `sk-orca-`)
+* A good starting `Model` is `orcarouter/auto`, which routes each request to the best available model
+
 For other AI service:
 
 * The `Server` should fill in a URL equivalent to OpenAI's `https://api.openai.com/v1`. For example, when using `Ollama`, it should be `http://localhost:11434/v1` instead of `http://localhost:11434/api/generate`