Add client examples reference to README.md

- Document available API client examples in docs/client-examples/
- List all 5 supported languages with links to files

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -103,6 +103,18 @@ When a customer purchases a licensed product, they must enter the domain where t
 
 Full API documentation available in `openapi.json` (OpenAPI 3.1 specification).
 
+### Client Examples
+
+Ready-to-use API client examples are available in `docs/client-examples/`:
+
+- **cURL** - Shell script examples ([curl.sh](docs/client-examples/curl.sh))
+- **PHP** - Client class with examples ([php-client.php](docs/client-examples/php-client.php))
+- **Python** - Client class with dataclasses ([python-client.py](docs/client-examples/python-client.py))
+- **JavaScript** - Browser and Node.js client ([javascript-client.js](docs/client-examples/javascript-client.js))
+- **C#** - Async client with System.Text.Json ([csharp-client.cs](docs/client-examples/csharp-client.cs))
+
+All examples include rate limit handling (HTTP 429) and demonstrate the validate, status, and activate endpoints.
+
 ### Validate License
 
 Validate a license key for a specific domain.