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/assets/javascripts/application.js

@@ -13,10 +13,6 @@
 //= require rails-timeago
 //= require locales/jquery.timeago.de.js
 //
-// lib/assets
-//= require flash
-//= require color_mode_picker
-//
 // app/assets
 // --> Include some assets first, as they are used by other assets.
 // --> Hence, the order specified here is important.

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';