add comment to rollup config

Author: Lms24

packages/replay/rollup.npm.config.js

@@ -8,6 +8,8 @@ export default makeNPMConfigVariants(
         // set exports to 'named' or 'auto' so that rollup doesn't warn about
         // the default export in `worker/worker.js`
         exports: 'named',
+        // set preserveModules to false because for Replay we actually want
+        // to bundle everything into one file.
         preserveModules: false,
       },
     },