Add layer generation scripts corresponding to the sample layers on the ATT&CK Navigator repo

[isaisabel]

As a user of the ATT&CK Navigator, I want to learn how to write scripts to generate layers from the STIX data on MITRE/CTI.

The ATT&CK Navigator includes sample layers in /layers/data/samples. There are scripts corresponding to these layers. We should release those scripts on this repository and create references to them from the ATT&CK Navigator repository.