Add API key access link to README

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Co-Authored-By: Claude <[email protected]>

Author: chengzeyi

README.md

@@ -41,7 +41,7 @@ print(output["outputs"][0])  # Output URL
 
 ### Authentication
 
-Set your API key via environment variable:
+Set your API key via environment variable (You can get your API key from [https://wavespeed.ai/accesskey](https://wavespeed.ai/accesskey)):
 
 ```bash
 export WAVESPEED_API_KEY="your-api-key"