Initial commit of rig project create example. [WIP]

[grayside]

Demonstration/example of the output on rig project create.

Note that:

1. Recent changes in Lightning dependencies/drush/Drupal core mean I suspect composer install will not work with the current code.
2. Updates to support generation with Particle instead of Pattern Lab Starter haven't trickled in yet, so I did not include theme generation & support.

Still, seems potentially valuable. I've left the README in default generated state, but will probably circle back later to add more clarification on just what this example is all about.