[Javascript] using browersify on javascript client

Description

I tried to follow the instruction present in the README.md file generated by the generator, in order to get a client that is usable in the browser

browserify index.js > bundle.js

but the command failed indicating

Error: Parsing file /home/.../petstore/javascript/src/index.js: 'import' and 'export' may appear only with 'sourceType: module' (16:0)
	at Deps.parseDeps (/usr/lib/node_modules/browserify/node_modules/module-deps/index.js:519:15)
	at getDeps (/usr/lib/node_modules/browserify/node_modules/module-deps/index.js:447:44)
	at /usr/lib/node_modules/browserify/node_modules/module-deps/index.js:430:38
	at ConcatStream.<anonymous> (/usr/lib/node_modules/browserify/node_modules/concat-stream/index.js:37:43)
	at emitNone (events.js:111:20)
	at ConcatStream.emit (events.js:208:7)
	at finishMaybe (/usr/lib/node_modules/browserify/node_modules/readable-stream/lib/_stream_writable.js:630:14)
	at endWritable (/usr/lib/node_modules/browserify/node_modules/readable-stream/lib/_stream_writable.js:638:3)
	at ConcatStream.Writable.end (/usr/lib/node_modules/browserify/node_modules/readable-stream/lib/_stream_writable.js:594:41)
	at DuplexWrapper.onend (/usr/lib/node_modules/browserify/node_modules/readable-stream/lib/_stream_readable.js:577:10)

Swagger-codegen version

The version is 3.0.27

java -jar swagger-codegen-cli.jar version
3.0.27

Swagger declaration file content or url

I'm using the petstore api
https://petstore.swagger.io/v2/swagger.json

Command line used for generation

java -jar swagger-codegen-cli.jar generate -i swagger.json -l javascript -o javascript

Steps to reproduce

cd javascript/src
browserify index.js > bundle.js

Related issues/PRs

No

Suggest a fix/enhancement

Start with javascript/src/index.js and the generated README, then reproduce the failure from javascript/src with browserify index.js > bundle.js. Trace the generated client entry point and its browser bundling instructions; done means the documented command completes without the import/export parsing error and produces bundle.js.