Move asset precompile config to config/manifest.js for Sprockets 4.

app/assets/config/manifest.js

@@ -0,0 +1,3 @@
+//= link_tree ../images
+//= link_directory ../javascripts .js
+//= link_directory ../stylesheets .css

app/assets/stylesheets/black.scss

@@ -9,4 +9,4 @@ $link-bgcolor: $link-color;
 $box-tablink-color: unset;
 
 // Import all components
-@import 'manifest';
+@import 'include/manifest';

app/assets/stylesheets/light_blue.scss

@@ -9,4 +9,4 @@ $link-bgcolor: unset;
 $box-tablink-color: lighten(#000, 85%);
 
 // Import all components
-@import 'manifest';
+@import 'include/manifest';

config/initializers/assets.rb

@@ -7,8 +7,3 @@ Rails.application.config.assets.version = '1.0'
 # Rails.application.config.assets.paths << Emoji.images_path
 # Add Yarn node_modules folder to the asset load path.
 Rails.application.config.assets.paths << Rails.root.join('node_modules')
-
-# Precompile additional assets.
-# application.js, application.css, and all non-JS/CSS in the app/assets
-# folder are already added.
-Rails.application.config.assets.precompile += %w( light_blue.css black.css print.css mobile.css jquery-ui/datepicker-*.js )