Add a small example for working out control keys (#192)

examples/keyboard.rs

@@ -0,0 +1,16 @@
+use std::io;
+
+use console::{Key, Term};
+
+fn main() -> io::Result<()> {
+    let term = Term::stdout();
+    term.write_line("Press any key. Esc to exit")?;
+    loop {
+        let key = term.read_key()?;
+        term.write_line(&format!("You pressed {:?}", key))?;
+        if key == Key::Escape {
+            break;
+        }
+    }
+    Ok(())
+}