Use of async_std::task::sleep instead of tokio::time::sleep in examples (#2912)

* Use of async_std::task::sleep instead of tokio::time::sleep

* Make the clock example run on wasm

* Add control_focus and eval examples to Cargo.toml

* Use web-time on desktop; It just falls back to std on non-wasm platforms

---------

Co-authored-by: Evan Almloff <evanalmloff@gmail.com>

examples/backgrounded_futures.rs

@@ -7,10 +7,11 @@
 //!
 //! This example is more of a demonstration of the behavior than a practical use case, but it's still interesting to see.
 
+use async_std::task::sleep;
 use dioxus::prelude::*;
 
 fn main() {
-    launch_desktop(app);
+    launch(app);
 }
 
 fn app() -> Element {
@@ -48,7 +49,7 @@ fn Child(count: Signal<i32>) -> Element {
 
     use_future(move || async move {
         loop {
-            tokio::time::sleep(std::time::Duration::from_millis(100)).await;
+            sleep(std::time::Duration::from_millis(100)).await;
             println!("Child")
         }
     });