Add variables-referencing-variables capability in Atomic

Describe the Problem

Variables do not have the ability to reference other variables. This is standard in every other design system.

Propose a Solution

Add variable-referencing-variables.

Additional Context

_No response_

Agreement

• I confirm I have read and followed all the guidelines and instructions outlined in the Feature Request form.
• I agree that my discussion may be closed without further action if it doesn't meet all the requirements outlined in the Feature Request form.