Module export problem

In order to get a more small size of bundle file, I include the original JsBarcode library from `src/JsBarcode.js`, but get the following error:

```
🚨 'default' is not exported by node_modules\jsbar
https://github.com/rollup/rollup/wiki/Troubleshootin
dule
src\index.js (1:7)
1: import JsBarcode from 'jsbarcode/src/JsBarcode';
```

Start with src/index.js and src/JsBarcode.js, then inspect how the Rollup build resolves the JsBarcode import and export. Reproduce the reported build error and confirm that the source import works while producing the intended smaller bundle.

Written by the indexing model from the issue text.