Copy index.d.ts to build folder on build

config/webpack.config.prod.js

@@ -21,6 +21,7 @@ const getClientEnvironment = require('./env');
 const ModuleNotFoundPlugin = require('react-dev-utils/ModuleNotFoundPlugin');
 const ForkTsCheckerWebpackPlugin = require('fork-ts-checker-webpack-plugin-alt');
 const typescriptFormatter = require('react-dev-utils/typescriptFormatter');
+const CopyWebpackPlugin = require('copy-webpack-plugin');
 const getPackageJson = require('./getPackageJson');
 
 
@@ -510,6 +511,12 @@ module.exports = {
     // https://github.com/jmblog/how-to-optimize-momentjs-with-webpack
     // You can remove this if you don't use Moment.js:
     new webpack.IgnorePlugin(/^\.\/locale$/, /moment$/),
+    new CopyWebpackPlugin([
+      {
+        from: `${paths.appSrcLibTypes}`,
+        to: paths.appLayoutsBuild
+      }
+    ]),
     // Generate a service worker script that will precache, and keep up to date,
     // the HTML & assets that are part of the Webpack build.
     /*new WorkboxWebpackPlugin.GenerateSW({