upgrade code to webpack v5

Ref: https://webpack.js.org/migrate/5/

Author: bpinto

lib/build.js

@@ -158,12 +158,11 @@ async function webpackConfig(
     entry: {},
     target: 'node',
     plugins: [
-      new webpack.IgnorePlugin(/vertx/),
+      new webpack.IgnorePlugin({ resourceRegExp: /vertx/ }),
       new webpack.DefinePlugin(defineEnv),
     ],
     output: {
       path: functionsPath,
-      filename: '[name].js',
       libraryTarget: 'commonjs',
     },
     optimization: {