examples: Add an example of using duck-typed interfaces

examples/duck-typed-interfaces/webpack.config.js

@@ -0,0 +1,10 @@
+const path = require('path');
+
+module.exports = {
+    entry: './index.js',
+    output: {
+        path: path.resolve(__dirname, 'dist'),
+        filename: 'index.js',
+    },
+    mode: 'development'
+};