Update starlette subdomain in docs (#2099)

Author: alDuncanson

docs/a2a.md

@@ -27,7 +27,7 @@ The library is designed to be used with any agentic framework, and is **not excl
 
 ### Design
 
-**FastA2A** is built on top of [Starlette](https://starlette.io), which means it's fully compatible with any ASGI server.
+**FastA2A** is built on top of [Starlette](https://www.starlette.io), which means it's fully compatible with any ASGI server.
 
 Given the nature of the A2A protocol, it's important to understand the design before using it, as a developer
 you'll need to provide some components:
@@ -66,7 +66,7 @@ pip/uv-add fasta2a
 
 The only dependencies are:
 
-- [starlette](https://starlette.io): to expose the A2A server as an [ASGI application](https://asgi.readthedocs.io/en/latest/)
+- [starlette](https://www.starlette.io): to expose the A2A server as an [ASGI application](https://asgi.readthedocs.io/en/latest/)
 - [pydantic](https://pydantic.dev): to validate the request/response messages
 - [opentelemetry-api](https://opentelemetry-python.readthedocs.io/en/latest): to provide tracing capabilities