Remove optional "x" from module rules. This was related to React inte…

…gration with Webpack, which doesn't apply.

webpack.config.js

@@ -51,7 +51,7 @@ const baseConfig = {
     rules: [
       // all files with a `.ts` extension will be handled by `ts-loader`
       {
-        test: /\.(ts|js)x?$/,
+        test: /\.(ts|js)$/,
         loader: 'ts-loader',
         exclude: /node_modules/
       }