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/clock.rs

@@ -1,14 +1,14 @@
 //! A simple little clock that updates the time every few milliseconds.
 //!
-//! Neither Rust nor Tokio have an interval function, so we just sleep until the next update.
-//! Tokio timer's don't work on WASM though, so you'll need to use a slightly different approach if you're targeting the web.
 
 use dioxus::prelude::*;
+use tokio::time::sleep;
+use web_time::Instant;
 
 const STYLE: &str = asset!("./examples/assets/clock.css");
 
 fn main() {
-    launch_desktop(app);
+    launch(app);
 }
 
 fn app() -> Element {
@@ -16,12 +16,10 @@ fn app() -> Element {
 
     use_future(move || async move {
         // Save our initial timea
-        let start = std::time::Instant::now();
+        let start = Instant::now();
 
         loop {
-            // In lieu of an interval, we just sleep until the next update
-            let now = tokio::time::Instant::now();
-            tokio::time::sleep_until(now + std::time::Duration::from_millis(27)).await;
+            sleep(std::time::Duration::from_millis(27)).await;
 
             // Update the time, using a more precise approach of getting the duration since we started the timer
             millis.set(start.elapsed().as_millis() as i64);