Get value from ToggleData event

## Feature Request

The `details` HTML element triggers a `toggle` event whenever it is opened or closed. However, one doesn't know what happened in the `ontoggle` event listener.

```rust
use dioxus::prelude::*;

#[component]
pub fn ToggleMe() -> Element {
rsx! {
details {
ontoggle: move |event| {
// now what?
},

summary {
"Open me"
}
" simple text"
}
}
}

```

## Implement Suggestion

It would be nice to have a function `.is_open()`, akin to the `.checked()` function on the input element's event.

Start at the ToggleData event entry point and compare its API with the existing checked() function on input events. Add a way for the ontoggle listener to determine whether details is open, and verify that the event exposes the expected state.

Written by the indexing model from the issue text.