Add npm dependencies in the production image

[KevinMind]

Fixes: mozilla/addons#15314
Fixes: mozilla/addons#15315

Description

This stops the bleeding but we will need a better test for the production image that does not rely on mounted data.

Context

After moving node_modules to no longer be a dependency of /deps we need to explcitly copy both directories to the final production stage.

This was not caught so far because our CI checks are using make up which re-runs the build steps ensuring those files exist in the mount. We should run without a mount the same checks to verify the pure production image.

https://mozilla.sentry.io/issues/6254859352/?project=6224627&referrer=slack

Testing

You can run the build locally and inspect the files.. you cannot use make up for this because it mounts the files.

Checklist

• Add #ISSUENUM at the top of your PR to an existing open issue in the mozilla/addons repository.
• Successfully verified the change locally.
• The change is covered by automated tests, or otherwise indicated why doing so is unnecessary/impossible.
• Add before and after screenshots (Only for changes that impact the UI).
• Add or update relevant docs reflecting the changes made.