Fix GitHub Models docs links (#2135)

Author: DouweM

docs/api/providers.md

@@ -28,4 +28,6 @@
 
 ::: pydantic_ai.providers.heroku.HerokuProvider
 
+::: pydantic_ai.providers.github.GitHubProvider
+
 ::: pydantic_ai.providers.openrouter.OpenRouterProvider

docs/models/index.md

@@ -23,6 +23,7 @@ In addition, many providers are compatible with the OpenAI API, and can be used
 * [Together AI](openai.md#together-ai)
 * [Azure AI Foundry](openai.md#azure-ai-foundry)
 * [Heroku](openai.md#heroku-ai)
+* [GitHub Models](openai.md#github-models)
 
 PydanticAI also comes with [`TestModel`](../api/models/test.md) and [`FunctionModel`](../api/models/function.md)
 for testing and development.