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.

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({