newsletter: Add a note about transferable streams

Author: trflynn89

src/content/newsletters/2025-05-31.mdx

@@ -37,6 +37,14 @@ button to copy the code to the clipboard. We had previously implemented just one
 implemented the rest! These are `clipboard.read`, `clipboard.readText`, `clipboard.write`, and `clipboard.writeText`.
 And not to worry! These APIs have security built into them to protect users from malicious actors.
 
+### Transferable Streams
+
+Last month, we refined our [streams](https://developer.mozilla.org/en-US/docs/Web/API/Streams_API) implementation to be
+much better aligned with the spec. The last remaining feature that we hadn't implemented was
+[stream transfer](https://github.com/whatwg/streams/blob/main/transferable-streams-explainer.md). This allows web
+developers to transfer streams via `postMessage()` to, for example, a web worker. We've now implemented this feature,
+and as a result, we now have a complete streams implementation!
+
 ### Credits
 
 We'd like to thank everyone who contributed code this month: