refactor: Move Sprocket JS files to Webpack (Part 1)

JavaScript for RfCs, Flashes and the color mode can be moved without
modifications.

Relates to #3021

Author: arkirchner

app/javascript/application.js

@@ -88,3 +88,7 @@ window.ace = ace; // Publish ace in global namespace
 // Turbo
 import '@hotwired/turbo-rails';
 import './turbo-migration';
+
+// Import of Rails sprocket assets with minimal changes. After the initial migration these files should
+// be moved to an appropriate place after some adjustments to fit modern Rails JS.
+import 'sprocket_asset_import'

lib/assets/javascripts/color_mode_picker.js renamed to app/javascript/sprocket_asset_import/color_mode_picker.js

@@ -0,0 +1,4 @@
+import './flash'
+import './color_mode_picker'
+
+import './request_for_comments'