Tweak CLI command

Author: markerikson

src/app/reference/replay-cli/source-maps/page.md

@@ -23,6 +23,7 @@ You can upload source maps using the `replayio upload-source-maps` command in th
 The simplest usage will be running the following after your production JS build has finished.
 
 ```sh
+npm run build
 npx replayio upload-source-maps --group <Version or SHA> <buildOutputDir>
 ```