maybe crafty works like this

package.json

@@ -20,17 +20,19 @@
     "postcss-loader": "^3.0.0",
     "sass-loader": "^7.1.0",
     "style-loader": "^0.23.1",
+    "transform-loader": "^0.2.4",
 
     "autoprefixer": "^9.3.1",
+    "brfs": "^2.0.1",
     "node-sass": "^4.10.0",
     "precss": "^3.1.2",
     "webpack": "^4.25.1",
     "webpack-cli": "^3.1.2",
 
     "bootstrap": "^4.1.3",
+    "craftyjs": "^0.9.0",
     "jquery": "^3.3.1",
-    "popper.js": "^1.14.5",
-    "craftyjs": "^0.9.0"
+    "popper.js": "^1.14.5"
   },
 
   "dependencies": {

src/game.js

@@ -1,4 +1,6 @@
-import Crafty from 'craftyjs'
-import CONF from './game/config.coffee'
+import $ from 'jquery'
 
+$(() => {
+  require('craftyjs/dist/crafty.js')
   require('./game/test_entities.coffee')
+})

webpack.config.js

@@ -17,6 +17,10 @@ module.exports = {
 
   module: {
     rules: [
+      {
+        loader: "transform-loader?brfs",
+        enforce: "post"
+      },
 
       {
         test: /\.css$/,