Mathics3-Rubi repository created! Rubi discussion moved.

[rocky]

Thanks to @aravindh-krishnamoorthy, serious progress has been made in getting Rubi to work on Mathics3.

To facilitate working on Rubi for Mathics3, a new repository under the Mathics3 organization has been created.

The discussion that had been started here in "core" has been moved to there.

If you have questions, concerns, or comments about this, let me know.