Test using the supported way of compiling sass

[jcoyne]

There are warnings about sassc-rails being not supported since 2019 in https://guides.rubyonrails.org/asset_pipeline.html#cssbundling-rails

In rails 6:

The file /home/runner/work/blacklight/blacklight/.internal_test_app/app/assets/stylesheets/application.bootstrap.scss does not appear to exist

In rails 7.0:

$ esbuild app/javascript/*.* --bundle --sourcemap --format=esm --outdir=app/assets/builds --public-path=/assets
Error: R] No matching export in "node_modules/bootstrap/dist/js/bootstrap.esm.js" for import "default"

    app/javascript/application.js:5:7:
      5 │ import bootstrap from "bootstrap"
        ╵        ~~~~~~~~~