Procedural macros in Rust allow developers to extend the language and automate code generation. They are often used to create custom derive attributes or other annotations that modify or add to Rust's functionality.

In this challenge, you'll implement a procedural macro to derive a custom trait called Describe. The Describe trait should provide a method, describe, that returns a string containing the name of the struct and its fields with their values. This macro should generate an implementation of the trait automatically when applied to a struct.

Your task is to create a procedural macro named derive_describe that can be used to generate the Describe trait implementation for any struct. The generated describe method should return a string representation of the struct, including its name and all its fields with their respective values.

For example, applying the macro to a struct like:

#[derive(Describe)]
struct Point {
    x: i32,
    y: i32,
}

Should generate a Describe implementation such that:

let p = Point { x: 1, y: 2 };
assert_eq!(p.describe(), "Point { x: 1, y: 2 }");

1. The derive_describe macro should:

   • Generate the Describe trait implementation for the struct it is applied to.
   • Support structs with named fields. (Tuple structs or unit structs are not required for this challenge.)

2. The describe method should return a properly formatted string, including the struct name and fields with their values.

Procedural macros must be defined in a separate crate from the one where they are used. This is because procedural macros are compiled to a shared library that is loaded by the Rust compiler at compile time. The shared library must be compiled before the crate that uses the macro.

In your Cargo.toml, you should define a new crate for the procedural macro:

[lib]
proc-macro = true

This is already done for this challenge, but it's important to understand the setup.