pub fn insert<T: Into<Value>>(self, val: T) -> &'a mut Value {
        let obj = unsafe { self.dormant_obj.awaken() };
        #[cfg(not(feature = "sort_keys"))]
        obj.reserve(1);
        let val = obj.0.insert(self.key.as_str().unwrap(), val.into());
        val
    }
Insert a value into the vacant entry and return a mutable reference to it.

# Examples

```
use sonic_rs::{json, object, value::object::Entry};

let mut obj = object! {};

if let Entry::Vacant(entry) = obj.entry(&"hello") {
assert_eq!(entry.insert(1), &1);
}

if let Entry::Vacant(entry) = obj.entry(&"world") {
assert_eq!(entry.insert(json!("woo").clone()), "woo");
}

assert_eq!(obj.get(&"hello").unwrap(), 1);
assert_eq!(obj.get(&"world").unwrap(), "woo");
```
src/value/object.rs