Date macro code - I needed this, so thought I would give it back to the community

[roboweaver]

Issue #, if available:

Description of changes: Example of a macro for inserting ISO dates in a template. Useful for policies on SSM parameters for instance.

Details are in the README.md

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[roboweaver]

Anybody there - I have been using this macro locally, suits my purpose. This has been open since November.