Replace babel/polyfill w/ core-js v3.

Babel versions above 7.4 recommend using new core-js polyfill over
deprecated babel/polyfill. Also updated babel/core and babel/preset-env.
Added babelrc for defined config of corejs version & targeted browsers.

.babelrc

@@ -0,0 +1,15 @@
+{
+  presets: [
+   [
+     "@babel/preset-env",
+      {
+        modules: false,
+        targets: {
+          browsers: ["IE 11", "> 5%"]
+        },
+        useBuiltIns: "usage",
+        corejs: "3"
+      }
+    ]
+  ]
+}

config/vinlottis.config.js

@@ -5,7 +5,7 @@ const helpers = require("./helpers");
 
 const VinlottisConfig = {
   entry: {
-    vinlottis: ["@babel/polyfill", helpers.root("src", "vinlottis-init")]
+    vinlottis: helpers.root("src", "vinlottis-init")
   },
   optimization: {
     minimizer: [

config/webpack.config.dev.js

@@ -41,7 +41,7 @@ let webpackConfig = merge(commonConfig(true), {
 
 webpackConfig = merge(webpackConfig, {
   entry: {
-    main: ["@babel/polyfill", helpers.root("src", "vinlottis-init")]
+    main: helpers.root("src", "vinlottis-init")
   },
   plugins: [
     new HtmlPlugin({

package.json

@@ -12,7 +12,6 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
-    "@babel/polyfill": "~7.2",
     "@zxing/library": "^0.15.2",
     "canvas-confetti": "^1.2.0",
     "chart.js": "^2.9.3",
@@ -39,15 +38,16 @@
     "web-push": "^3.4.3"
   },
   "devDependencies": {
-    "@babel/core": "~7.2",
+    "@babel/core": "~7.12",
     "@babel/plugin-proposal-class-properties": "~7.3",
     "@babel/plugin-proposal-decorators": "~7.3",
     "@babel/plugin-proposal-json-strings": "~7.2",
     "@babel/plugin-syntax-dynamic-import": "~7.2",
     "@babel/plugin-syntax-import-meta": "~7.2",
-    "@babel/preset-env": "~7.3",
+    "@babel/preset-env": "~7.12",
     "babel-loader": "~8.0",
     "compression-webpack-plugin": "^3.1.0",
+    "core-js": "3",
     "cross-env": "^6.0.3",
     "css-loader": "^3.2.0",
     "file-loader": "^4.2.0",

src/vinlottis-init.js

@@ -4,6 +4,8 @@ import { routes } from "@/router.js";
 import Vinlottis from "@/Vinlottis";
 import VueAnalytics from "vue-analytics";
 
+import "core-js/stable"; // babel polyfill
+
 Vue.use(VueRouter);
 Vue.use(VueAnalytics, {
   id: "UA-156846886-1"