Setup Bootstrap tree shaking

app/assets/javascripts/commons/bootstrap.js

 import $ from 'jquery';
 
 // bootstrap jQuery plugins
-import 'bootstrap';
+import 'bootstrap/js/dist/alert';
+import 'bootstrap/js/dist/button';
+import 'bootstrap/js/dist/modal';
+import 'bootstrap/js/dist/dropdown';
+import 'bootstrap/js/dist/tab';
+import 'bootstrap/js/dist/tooltip';
 
 // custom jQuery functions
 $.fn.extend({

ee/app/assets/javascripts/main_ee.js

 import $ from 'jquery';
+import 'bootstrap/js/dist/modal';
 import initEETrialBanner from 'ee/ee_trial_banner';
 import trackNavbarEvents from 'ee/event_tracking/navbar';
 import initNamespaceStorageLimitAlert from 'ee/namespace_storage_limit_alert';