In the pipeline Snippet Generator, the withNPM step does not generate the list of npmrc Config items.

Steps to reproduce:

1. Install pipeline-npm, nodejs, and config-file-provider plugins
2. Create a folder
3. Create a pipeline job inside the folder
4. Inside the folder, go to Config Files -> add a new config.
5. Create an Npm config file and save it 
6. Inside the pipeline job configuration, select Pipeline Script then Pipeline Syntax
7. Under Snippet Generator, select withNPM: Provide NPM Environment
8. Click dropdown for npmrc Config. See that there are no options listed.