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/future.rs

@@ -3,11 +3,11 @@
 //! use_future won't return a value, analogous to use_effect.
 //! If you want to return a value from a future, use use_resource instead.
 
+use async_std::task::sleep;
 use dioxus::prelude::*;
-use std::time::Duration;
 
 fn main() {
-    launch_desktop(app);
+    launch(app);
 }
 
 fn app() -> Element {
@@ -16,7 +16,7 @@ fn app() -> Element {
     // use_future will run the future
     use_future(move || async move {
         loop {
-            tokio::time::sleep(Duration::from_millis(200)).await;
+            sleep(std::time::Duration::from_millis(200)).await;
             count += 1;
         }
     });
@@ -24,7 +24,7 @@ fn app() -> Element {
     // We can also spawn futures from effects, handlers, or other futures
     use_effect(move || {
         spawn(async move {
-            tokio::time::sleep(Duration::from_secs(5)).await;
+            sleep(std::time::Duration::from_secs(5)).await;
             count.set(100);
         });
     });