webui generates es2017 output and removes confusing babel config

Babel dependencies were configured but not actually used by any webui bundles since they are all typescript.
Typescript was not configured to output using the latest features supported by v8.

This re-configuration ensures:
- TS output is transpiled to es2017 JS and no further, which should allow for optimizations. Previously it was es5.
- es module syntax is preserved, allowing webpack to tree shake
- async lazy-load import() syntax is preserved, allowing webpack to perform chunking

This also fixes an issue whereby linking brave-ui dependency from a local path would prevent webui compilation.

components/brave_rewards/resources/ui/components/pageWallet.tsx

@@ -24,7 +24,7 @@ import * as utils from '../utils'
 import WalletOff from 'brave-ui/features/rewards/walletOff'
 import ModalAddFunds from 'brave-ui/features/rewards/modalAddFunds'
 
-import clipboardCopy = require('clipboard-copy')
+const clipboardCopy = require('clipboard-copy')
 
 interface State {
   activeTabId: number
@@ -74,10 +74,14 @@ class PageWallet extends React.Component<Props, State> {
     })
   }
 
-  onModalBackupOnCopy = (backupKey: string) => {
-    const success = clipboardCopy(backupKey)
+  onModalBackupOnCopy = async (backupKey: string) => {
     // TODO(jsadler) possibly flash a message that copy was completed
-    console.log(success ? 'Copy successful' : 'Copy failed')
+    try {
+      await clipboardCopy(backupKey)
+      console.log('Copy successful')
+    } catch (e) {
+      console.log('Copy failed')
+    }
   }
 
   onModalBackupOnPrint = (backupKey: string) => {

components/common/locale.ts

@@ -27,4 +27,3 @@ export const getLocale = (key: string, replacements?: Record<string, string>) =>
   return returnVal
 }
 
-module.exports = { getLocale }

components/webpack/webpack.config.js

@@ -23,14 +23,6 @@ module.exports = (env, argv) => ({
         test: /\.tsx?$/,
         loader: 'awesome-typescript-loader'
       },
-      {
-        test: /\.js$/,
-        loader: 'babel-loader',
-        exclude: /node_modules/,
-        query: {
-          presets: ['react-optimize']
-        }
-      },
       {
         test: /\.less$/,
         loader: 'style-loader!css-loader?-minimize!less-loader'