Revise deprecation warning for legacy package

Updated deprecation notice to recommend migration to serpapi-python and provided information on documentation compatibility.

Author: schaferyan

README.md

@@ -2,9 +2,10 @@
 #
 
 > [!WARNING]
-> This package is **deprecated** in favor of [serpapi-python](https://github.com/serpapi/serpapi-python).
-> Please migrate to the newer implementation.
-
+> This package will soon be **deprecated** in favor of [serpapi-python](https://github.com/serpapi/serpapi-python).
+> We recommend migrating to the newer implementation to ensure continued support and access to the latest features and improvements.
+> 
+> Please note: the current documentation, examples, and integrations on https://serpapi.com/ are written for this (legacy) package and are not yet compatible with the new library. Updated documentation for `serpapi-python` will be published soon.
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