You're already familiar with implementing traits in Rust, let's explore some special traits from the standard library - specifically those that allow operator overloading through the std::ops module.

One such trait is Add, which allows you to implement custom behavior for the + operator. This is particularly useful when working with types that have a natural addition operation, like measurements or mathematical types.

Let's implement custom addition between different units of measurement. You'll create a system where you can add meters to millimeters, with automatic unit conversion.

Your job is to implement a Millimeters struct and a Meters struct, then implement the Add trait to allow adding a Meters value to a Millimeters value. The result should be a new Millimeters value.

• Define two structs: Millimeters and Meters, each holding a single u32 value
• Implement the Add<Meters> trait for Millimeters to handle addition with Meters
• Conversion rules:
  • 1 meter = 1000 millimeters
  • When adding, convert meters to millimeters first
  • Return the result as Millimeters

If you're stuck, here are some hints to help you solve the challenge!