Adding timeout extension method to Future trait

[miker1423]

This would close issue #564

[miker1423]

Hello! I got two errors like the following on the rust fmt check, but I don't understand what I should do to solve them.

 #[test]
 fn should_not_timeout() {
-    task::block_on(async {        
+    task::block_on(async {
         let fut = future::ready(0);
         let dur = Duration::from_millis(100);
         let res = fut.timeout(dur).await;
Diff in /home/runner/work/async-std/async-std/tests/timeout_future.rs at line 25:

[k-nasa]

@miker1423
My editor highlights unnecessary spaces at the end of lines. Maybe this is the cause of the error?
Can I fix it by running cargo fmt?

[k-nasa]

The merge is coming soon! Please make some corrections.

[k-nasa]

@miker1423
Please make a few corrections!
I think the rest is perfect.

Then, please merge or rebase the master branch.

[k-nasa]

Excellent; thanks heaps!