doc: update readme add async open router

README.md

@@ -629,7 +629,9 @@ print(tokenizer.decode(outputs[0]))
 
 
 ## Utilize free open-source LLM API through [Open Router](https://openrouter.ai/)
-OpenRouter offers temporary free inference for select models. Obtain an API key from [Open Router API](https://openrouter.ai/keys) and check free models at [Open Router models](https://openrouter.ai/docs#models). Use models with a 0-dollar token cost primarily; other models may incur charges. See more [free open-source LLM API guide](https://github.com/dsdanielpark/Gemini-API/blob/main/documents/README_OPENROUTER.md)
+OpenRouter offers temporary free inference for select models. Obtain an API key from [Open Router API](https://openrouter.ai/keys) and check free models at [Open Router models](https://openrouter.ai/docs#models). Use models with a 0-dollar token cost primarily; other models may incur charges. See more at [free open-source LLM API guide](https://github.com/dsdanielpark/Gemini-API/blob/main/documents/README_OPENROUTER.md).
+
+**Sync client is favored over async for Gemini due to rate limiting and blocking issues**, but OpenRouter offers reliable open-source LLMs for [async implementation](https://github.com/dsdanielpark/Gemini-API/blob/main/documents/README_OPENROUTER.md#openrouter-async-api-client).
 
 ```python
 from gemini import OpenRouter