Note we're adding the icons in English on both the `sdg/en/` folder and
the `sdg/default/` folder. The latter stores the default icons when the
desired language does not have a fallback with an icon folder.
Also note we need to explicitely add the images to the asset pipeline
because they've been added to the `vendor/` folder; for some reason,
everything works properly without adding them to the asset pipeline if
we use the `app/` folder instead.
Internet Explorer 9 was released eight years ago. Besides that, we don't
really support IE8 anyway, since we show a popup to IE8 users saying
we don't support it, we haven't maintained the IE8-specific CSS file for
years, and we don't test our JavaScript against IE8.
Rails 5 changed the initialization order, and now our initializers were
running before the `append_assets_path` initializer for each engine,
which prepended application assets to the custom assets we prepended in
the initializer.
Moving the code to the `config.after_initialize` code didn't work
either, since the paths added there were ignored by the application.
Adding another initializer to the Rails Engine is a hack, but solves the
problem.
