Please change the function signature of `dioxus::server::router` to allow users to set the state type

## Feature Request

I want to be able to set the state type on the router that's created when using the `dioxus::server::router` function.

## Implement Suggestion

The function is located in https://github.com/DioxusLabs/dioxus/blob/main/packages/fullstack-server/src/launch.rs

line 96.

change it from:

```rust
pub fn router(app: fn() -> Element) -> Router {
//....
}
```

to:

```rust
pub fn router(app: fn() -> Element) -> Router { // Setting the default to `()` should ensure compatability with existing apps
//....
}
```

That way I can do this:

```rust
dioxus::server::router::(App).with_state(store) // a struct wrapped in an Arc
```

You'll probably have to update some of the other functions that expect just a `Router` like `serve`.