module.exports = Package[‘mongo’]; Package not defined.

I'm trying to use webpack-meteor-externals npm package with Cypress, which already has a version of webpack-processor (https://github.com/cypress-io/cypress-webpack-preprocessor) available.

However, when I try
```
const meteorExternals = require('webpack-meteor-externals');
//...
externals: [
meteorExternals()
]
//...
```
I get an error message that says Package in "module.exports = Package[‘mongo’]" is not defined. Without webpack-meteor-externals, I get an error saying "meteor/mongo" module is not found.

Any suggestions?

Reproduce the Cypress setup shown in the issue, beginning with require('webpack-meteor-externals') and the externals configuration. Compare the `module.exports = Package['mongo']` failure with the `meteor/mongo` resolution failure; done means the Cypress webpack build resolves the module without a `Package is not defined` error.

Written by the indexing model from the issue text.