Add migration note at top of page

Author: Swimburger

fern/products/sdks/overview/typescript/publishing-to-npm.mdx

@@ -7,6 +7,10 @@ Publish your public-facing Fern TypeScript SDK to the [npmjs
 registry](https://www.npmjs.com/). After following the steps on this page,
 you'll have a versioned package published on npm.
 
+<Warning title="Already publishing to npm?">
+If you're currently using token-based authentication, npmjs is deprecating long-lived tokens in early 2025. See [Migrating from token-based to OpenID Connect (OIDC) publishing](#migrating-from-token-based-to-oidc-publishing) to upgrade to the more secure OIDC authentication.
+</Warning>
+
 <Frame>
 	<img src="assets/npm-packages.png" alt="Versioned package published on npmjs.com" />
 </Frame>