add note to readme (#110)

Author: sargunv

README.md

@@ -14,6 +14,11 @@ Serialization], and coroutines.
 
 ## Usage
 
+> [!IMPORTANT]
+>
+> The currently published version is the old JVM-only version based on OkHttp.
+> See the snapshot builds on GitHub packages for the KMP build.
+
 - [Documentation]
 - [API Reference]