Add tenacity utilities/integration

Author: dmontagu

docs/api/tenacity.md

@@ -0,0 +1,23 @@
+# `pydantic_ai.tenacity`
+
+## Setup
+
+To use the tenacity integration, you need to install the `tenacity` dependency:
+
+```bash
+pip install tenacity
+```
+
+## Overview
+
+The `pydantic_ai.tenacity` module provides HTTP transport wrappers and wait strategies that leverage the tenacity
+library to add convenient retry behavior to HTTP requests. This is particularly useful for handling transient failures
+like rate limits, network timeouts, or temporary server errors.
+
+The module includes:
+- **Transport Classes**: Wrap existing HTTP transports to add retry functionality
+- **Wait Strategies**: Smart waiting that respects HTTP headers like `Retry-After`
+
+For detailed usage examples and patterns, see the [HTTP Request Retries](../retries.md) guide.
+
+::: pydantic_ai.tenacity