Enums are a fundamental feature in Rust that let you define a type that can be one of several distinct variants. Enums make it easier to represent a set of related states or options cleanly and effectively.

In this challenge, you will implement a simple TrafficLight enum to represent the states of a traffic light: Red, Yellow, and Green. Each variant will be a unit struct with no associated data.

Create an enum TrafficLight with three variants:

• Red representing the red light.
• Yellow representing the yellow light.
• Green representing the green light.

Write a function light_action that takes a TrafficLight and returns a string describing the action associated with the light.

• For Red, return "Stop".
• For Yellow, return "Caution".
• For Green, return "Go".