The root cause here is the same as #4095
The failing `loadModule` call will return `undefined` for a js config
read operation, which later caused config being overwritten.
* feat(generator): allow plugins to modify how configs are extracted
* refactor(cli): change addConfigTransform parameters
Allow plugin author to set config 'descriptions' instead of implementing their own transform functions.
* fix(cli): fix missed issues from changing types from array to set
* fix: use reserved config transforms to check in API
* fix: lines dedupe
* feat(cli): When selecting "separate config files",
cli should create .browserslistrc file
close#1236
* test(cli): add test for extracting .browserslistrc
