JavaScript files are not productionized

The custom JavaScript files for the website are not minified, bundled, or productionized in any way. They're served with static names, e.g. language-switcher.js. As a result, the browser loads cached versions of the files, even after we deploy changes. We should minify and bundle the JS files, and then deploy them with a GUID in the filename.

Hugo supports JavaScript building, so that might provide a solution.

As an alternative fix, we could see if the config on the Cloud Storage bucket can be changed in some way to prevent the aggressive caching. The browser seems to reload JS files on the staging server, which could indicate a difference in config between the staging bucket and prod bucket.