Add instructions about precompiling assets to README

Thanks to @brtz for catching this!

Author: rosa

README.md

@@ -32,7 +32,7 @@ And that's it. With this alone, you should be able to access Mission Control Job
 
 ### API-only apps or apps using `vite_rails` and other asset pipelines outside Rails
 
-If you want to use this gem with an [API-only Rails app](https://guides.rubyonrails.org/api_app.html) or an app that's using `vite_ruby`/`vite_rails`, or some other custom asset pipeline different from Sprockets and Propshaft, you need just one more thing: configure an asset pipeline so you can serve the JavaScript and CSS included in this gem. We recommend to use [`Propshaft`](https://github.com/rails/propshaft). You simply need to add this line to your application's Gemfile:
+If you want to use this gem with an [API-only Rails app](https://guides.rubyonrails.org/api_app.html) or an app that's using `vite_ruby`/`vite_rails`, or some other custom asset pipeline different from Sprockets and Propshaft, you need one more thing: configure an asset pipeline so you can serve the JavaScript and CSS included in this gem. We recommend to use [`Propshaft`](https://github.com/rails/propshaft). You simply need to add this line to your application's Gemfile:
 
 ```ruby
 gem "propshaft"
@@ -43,7 +43,16 @@ Then execute
 $ bundle install
 ```
 
-And you should be ready to go.
+Then, make sure you add a step to your deployment pipeline to precompile assets:
+```
+RAILS_ENV=production rails assets:precompile
+```
+
+For example, if you're using the Dockerfile generated by Rails with an API-only app or having skipped the assets pipeline, re-add:
+```
+# Precompiling assets for production without requiring secret RAILS_MASTER_KEY
+RUN SECRET_KEY_BASE_DUMMY=1 ./bin/rails assets:precompile
+```
 
 *Note: Legacy CSS bundlers `sass-rails` and `sassc-rails` may fail to compile some of the CSS vendored into this library from [Bulma](https://github.com/jgthms/bulma), which was created in [Dart SASS](https://sass-lang.com/dart-sass/). You will therefore need to upgrade to `dartsass-rails` or some library that relies on it, like `cssbundling-rails`.*