Prior to ab123a3, this guide mentioned
that three gems (sass-rails, uglifier, and coffee-rails) would be added
to the Gemfile by default, unless the `--skip-sprockets` option was
used when generating the application.
However, ab123a3 removed uglifier and
coffee-rails from the guide (to reflect the switch to webpacker for
managing javascript in rails 6). Now that only sass-rails is left, the
guide should say "adding this to your Gemfile" instead of "adding them
to your Gemfile" and "add that gem" instead of "add those gems".

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The original text "used by Sprockets for asset compression" was written
when this sentence was summarizing the purpose of three gems:
sass-rails, uglifier, and coffee-rails.
However, ab123a3 removed uglifier and
coffee-rails from this sentence. Now that only sass-rails is left, we
can be more specific about what it is used for: compiling Sass
stylesheets.

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We link to the sprockets-rails repository in the preceding paragraph,
so it seems appropriate to also link to the sass-rails repository in
this paragraph. And since readers of this guide may not know what Sass
is, it also seems appropriate to link to the sass-lang.com website.

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Co-Authored-By: Eugene Kenny <elkenny@gmail.com>

of the Asset Pipeline guide

This section previously declared that the Rails controller generator
generated an `app/assets/javascripts/projects.coffee` and an
`app/assets/stylesheets/projects.scss` file. Then, in
ab123a3, we removed the assertion that
`app/assets/javascripts/projects.coffee` would be generated (to reflect
the switch to webpacker for managing javascript in Rails 6). However,
the preceding sentence and the subsequent paragraph were still written
with the assumption that a CoffeeScript file would be generated.

Now we've reworded those parts to be consistent with the fact that Rails
no longer generates a CoffeeScript file.

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As of rails/sass-rails@409d871
sass-rails no longer uses the `sass` gem (which is no longer
maintained; it has been replaced by the `sassc` gem). Thus, the rails
guides should not mention the `sass` gem specifically. Instead, they can
continue to reference the `sass-rails` gem.

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