Update .changeset/loud-radios-change.md

Co-authored-by: Alexander Marks <aomarks@google.com>

.changeset/loud-radios-change.md

@@ -2,4 +2,6 @@
 '@lit-labs/ssr': major
 ---
 
-dom shim does not expose the window object
+The Lit SSR DOM shim no longer defines a global `window` variable. This was removed to improve compatibility with libraries that detect whether they are running in Node vs the browser by checking for the presence of `window`.
+
+If you have code that runs during SSR which depends on the presence of `window`, you can either replace `window` with `globalThis`, or use `isSsr` to avoid running that code on the server (see https://lit.dev/docs/ssr/authoring/#browser-only-code).