Add support for attaching event listeners to the global window

## Feature Request

It's common to want to attach event listeners to the global window. For example, a custom slider element will want to listen to mousedown locally on the slider, but mousemove globally on the window.

Svelte has a [`svelte:window`](https://learn.svelte.dev/tutorial/svelte-window) special element for exactly these use cases.

## Implement Suggestion

Taking a cue from svelte, we could add something like a window special element that events can be attached to:
```rust
rsx! {
dioxus:window {
onmousemove: move |event| handle_mousemove(event)
}
div {
id: "slider",
onmousedown: move |event| handle_mousedown(event),
...
}
}
```

We could also introduce a new `use_window_event` hook or something similar.