fix webpack externals

Signed-off-by: Jari Kolehmainen <jari.kolehmainen@gmail.com>

webpack.main.ts

@@ -26,7 +26,7 @@ export default function (): webpack.Configuration {
       __filename: false,
     },
     externals: [
-      nodeExternals
+      nodeExternals()
     ],
     module: {
       rules: [