Remove Esprima from the js-yaml bundle.

According to the `js-yaml` docs, it is only needed if you are trying
to parse JS functions in/out of JSON, which we are not doing.

webpack.base.js

@@ -61,6 +61,7 @@ module.exports = {
     ],
   },
   plugins: [
+    new webpack.IgnorePlugin(/^esprima$/, /js-yaml/), // Ignore Esprima import for js-yaml
     new webpack.IgnorePlugin(/^\.\/locale$/, /moment$/), // Ignore all optional deps of moment.js
     new webpack.ProvidePlugin({
       fetch: 'imports-loader?this=>global!exports-loader?global.fetch!whatwg-fetch',