Highlight default enum variant

[omid]

Since Rust has introduced #[default], can we hightlight it in the doc?
Like this one:

#[derive(Default)]
enum Status {
    #[default]
    Active,
    Inactive,
}

For other type of default definition of enums, it can be hard! For example, the following code, can be hard:

#[derive(...)]
enum Status {
    Active,
    Inactive,
}

impl Default for Status {
    fn default() -> Self {
        serde::from_str("active").unwrap()
    }
}

or:

#[derive(...)]
enum Status {
    Active,
    Inactive,
}

impl Default for Status {
    fn default() -> Self {
        if env!("ENV") == "prod" {
            Self::Inactive
        } else {
            Self::Active
        }
    }
}

We can ignore these cases.

[omid]

I think it's related to cargo doc itself, not here