Move d3 to package.json and include I18n JS library though Gemfile

Also, update bundle to make it installable again (a version had been removed)

package.json

@@ -1,9 +1,10 @@
 {
   "dependencies": {
-    "@rails/webpacker": "3.5",
+    "@rails/webpacker": "4.0",
     "bootstrap": "^4.1.3",
     "bootswatch": "^4.1.3",
     "chosen-js": "^1.8.7",
+    "d3": "^5.9.1",
     "d3-tip": "^0.9.1",
     "font-awesome": "^4.7.0",
     "highlight.js": "^9.12.0",
@@ -17,7 +18,7 @@
     "webpack-merge": "^4.1.4"
   },
   "devDependencies": {
-    "webpack-dev-server": "2.11.2"
+    "webpack-dev-server": "3.2.1"
   },
   "scripts": {
     "webpack": "./bin/webpack",