Respect `main` package.json parameter if it exists for Node.js project

[akalipetis]

Currently, we only check the index.js file and the start package.json script when we initialize the configuration for an Express Node.js project. We should also make use of the main¹ package.json property instead of the static index.js file.

Footnotes

1. https://docs.npmjs.com/cli/v10/configuring-npm/package-json#main ↩

[akalipetis]

Accidental duplicate for #160