Configure builds

- Create `dartsass.builds` initializer and add all Sass files to be compiled. See https://github.com/rails/dartsass-rails#configuring-builds
- Create .keep
- Update manifest file to use /builds directory
- Ignore /builds

.gitignore

@@ -11,6 +11,8 @@ coverage
 
 # Ignore compiled assets
 /public/assets
+/app/assets/builds/*
+!/app/assets/builds/.keep
 
 # vim swap files and tags
 *.sw[a-z]

app/assets/config/manifest.js

@@ -1,5 +1,5 @@
 //= link_tree ../images
-//= link application.css
+//= link_tree ../builds
 //= link application.js
 //= link es6-components.js
 //= link domain-config.js

config/initializers/dartsass.rb

@@ -0,0 +1,8 @@
+APP_STYLESHEETS = {
+  "application.scss" => "application.css",
+}.freeze
+
+all_stylesheets = APP_STYLESHEETS.merge(GovukPublishingComponents::Config.all_stylesheets)
+Rails.application.config.dartsass.builds = all_stylesheets
+
+Rails.application.config.dartsass.build_options << " --quiet-deps"