Add Bootstrap JS/CSS

css/bootstrap.scss

+@import "~bootstrap/scss/bootstrap";

js/bootstrap.js

+// Import ECMAScript modules
+import {$,jQuery} from 'jquery';
+import 'bootstrap';
+
+// Import SASS modules
+import './../css/bootstrap.scss';
+
+// Custom code
+

package.json

 {
   "devDependencies": {
     "@symfony/webpack-encore": "^0.27.0",
+    "bootstrap": "^4.3.1",
+    "jquery": "^3.4.1",
     "node-sass": "^4.12.0",
+    "popper.js": "^1.15.0",
     "sass-loader": "^7.1.0"
   }
 }

webpack.config.js

@@ -8,6 +8,7 @@ Encore
     // only needed for CDN's or sub-directory deploy
     //.setManifestKeyPrefix('build/')
 
+    .addEntry('bootstrap', './js/bootstrap.js')
     .addStyleEntry('aether-mediawiki', './css/aether-mediawiki.scss')
 
     // .enableSingleRuntimeChunk()