docs: add universal guide (#18707)

- based on original effort in PR 17573

PR Close #18707

aio/content/examples/universal/webpack.config.universal.js

@@ -0,0 +1,40 @@
+const ngtools = require('@ngtools/webpack');
+const webpack = require('webpack');
+
+module.exports = {
+  devtool: 'source-map',
+// #docregion entry
+  entry: {
+    main: [
+      './src/universal/app-server.module.ts',
+      './src/universal/server.ts'
+    ]
+  },
+// #enddocregion entry
+  resolve: {
+    extensions: ['.ts', '.js']
+  },
+  target: 'node',
+// #docregion output
+  output: {
+    path: 'src/dist',
+    filename: 'server.js'
+  },
+// #enddocregion output
+// #docregion plugins
+  plugins: [
+    new ngtools.AotPlugin({
+      tsConfigPath: './tsconfig-universal.json'
+    })
+  ],
+// #enddocregion plugins
+// #docregion rules
+  module: {
+    rules: [
+      { test: /\.css$/, loader: 'raw-loader' },
+      { test: /\.html$/, loader: 'raw-loader' },
+      { test: /\.ts$/, loader: '@ngtools/webpack' }
+    ]
+  }
+// #enddocregion rules
+}