Merge pull request google-gemini#57 from pcoet/js-readme

added region tag to README for unimplemented features

Author: markmcd

javascript/README.md

@@ -14,3 +14,10 @@ For example:
 ## Format the code
 
     npm run format
+
+<!-- 
+[START update]
+// The Gen AI SDK for TypeScript and JavaScript is in preview.
+// Some features have not been implemented.
+[END update]
+ -->