Use An Object As A Value In MiniJinja

```cargo
[dependencies]
minijinja = { version= "2.3.1" }
```

#![allow(dead_code)]
#![allow(unused_variables)]

use minijinja::value::Object;
use minijinja::value::Enumerator;
use minijinja::{Environment, context, Value};
use std::sync::Arc;
use std::collections::BTreeMap;

#[derive(Clone, Debug)]
pub struct Site {
  // pages: Arc<Vec<Page>>
  pages: <Value as Page>::from_dyn_object
}

impl Object for Site {
    fn enumerate(self: &Arc<Self>) -> Enumerator {
        Enumerator::Str(&["pages"])
    }
}

#[derive(Clone, Debug)]
pub struct Page {
  sections: Arc<Vec<Section>>
}

impl Object for Page {
    fn enumerate(self: &Arc<Self>) -> Enumerator {
        Enumerator::Str(&["sections"])
    }
}

#[derive(Clone, Debug)]
pub struct Section {
  attrs: Arc<BTreeMap<Arc<String>, Arc<Span>>> 
}

impl Object for Section {
    fn enumerate(self: &Arc<Self>) -> Enumerator {
        Enumerator::Str(&["attrs"])
    }
}

#[derive(Clone, Debug)]
pub struct Span {
  text: Arc<String>
}

impl Object for Span {
    fn enumerate(self: &Arc<Self>) -> Enumerator {
        Enumerator::Str(&["text"])
    }
}


fn main() {
  let mut attrs = BTreeMap::new();
  attrs.insert(
    Arc::new("alfa".to_string()), 
    Arc::new(
      Span { 
        text: Arc::new("bravo".to_string()) 
      }
    )
  );

  let site = Arc::new(Site{
    //pages: Value::from_dyn_object(Arc::<Vec<Page>>::new(vec![]))
    pages: Value::from_dyn_object(vec![])


/*
      pages: Arc::new(vec![
        Page {
          sections: Arc::new(vec![
            Section {
              attrs: Arc::new(attrs)
            }
          ])
        }
      ])
      */

    }
  );

  let mut env = Environment::new();
  env.add_template(
    "hello", "Hello! {{ site }}"
  ).unwrap();
  let skeleton = env.get_template("hello").unwrap();
  let output = skeleton.render(
    context!(
      site => Value::from_dyn_object(site)
    )
  ).unwrap();
  println!("{}", output);

}