Need to emphasize importance of "Allow interactive with externa"

The readme lacks info about the extension usage details. The readme should emphasize using Client App rather than cloud version to avoid XSS issue, and also user need to check "Allow interactive with external" and "Show at header menu"

Open the repository README and review the extension usage section. Document that users should prefer the Client App over the cloud version to avoid the stated XSS issue, and explain how to enable “Allow interactive with external” and “Show at header menu.” Done means the usage guidance clearly includes all three points.

Written by the indexing model from the issue text.