Support ValueLike macro on plain enum

[chipsenkbeil]

For enums like

pub enum MyValueEnum {
    One,
    Two,
    Three,
}

should be able to derive a ValueLike impl of

impl ValueLike for MyValueEnum {
    fn into_value(self) -> Value {
        match self {
            Self::One => Value::Text(String::from("one")),
            Self::Two => Value::Text(String::from("two")),
            Self::Three => Value::Text(String::from("three")),
        }
    }

    fn try_from_value(value: Value) -> Result<Self, Value> {
        match value {
            Value::Text(x) => match x.as_str() {
                "one" => Ok(Self::One),
                "two" => Ok(Self::Two),
                "three" => Ok(Self::Three),
                _ => Err(Value::Text(x)),
            },
            x => Err(x),
        }
    }
}