refactor(examples): use crossterm event methods (#1792)

Crossterm 0.29 introduced methods to easily check / extract the event
type. E.g. as_key_press_event() and is_key_press(). This commit
updates the examples to use these methods instead of matching on
the event type. This makes the code cleaner and easier to read.

Also does a general cleanup of the event handling code in the examples.

examples/apps/widget-ref-container/src/main.rs

@@ -30,8 +30,8 @@ fn main() -> Result<()> {
 fn run(mut terminal: DefaultTerminal) -> Result<()> {
     loop {
         terminal.draw(render)?;
-        if matches!(event::read()?, event::Event::Key(_)) {
-            break Ok(());
+        if event::read()?.is_key_press() {
+            return Ok(());
         }
     }
 }