Option to create dioxus Router with AppState

## Feature Request

Right now it's not easy to add app state in the main module because `dioxus::server::router` returns Router<()>.

## Implement Suggestion

Current implementation:
```rust
pub fn router(app: fn() -> Element) -> Router {
let cfg = ServeConfig::new();
apply_base_path(
Router::new().serve_dioxus_application(cfg.clone(), app),
app,
cfg,
base_path().map(|s| s.to_string()),
)
}
```

We can change the current function to accept the State type:
```rust
pub fn router(app: fn() -> Element) -> Router {
let cfg = ServeConfig::new();
apply_base_path(
Router::new().serve_dioxus_application(cfg.clone(), app),
app,
cfg,
base_path().map(|s| s.to_string()),
)
}
```

Or create a new helper function (to not break current usage) like this:
```rust
pub fn router_with_state(app: fn() -> Element) -> Router {
let cfg = ServeConfig::new();
apply_base_path(
Router::new().serve_dioxus_application(cfg.clone(), app),
app,
cfg,
base_path().map(|s| s.to_string()),
)
}
```