add flag to optionally create two additional outputs, for dev- and prod- only dependencies

[sandacontiume]

Optionally generate additional output for

• development only dependencies, meaning, dependencies marked as "dev": true
• production only dependencies (non-dev), meaning, dependencies marked as "dev": false

[JeroenKnoops]

PR #23 does not create two files, but has an option to ignore the devDependencies. So running both versions and see the differences will be enough to create the separate files.