Write docs for iced_winit::Clipboard

Also explicitly allow the missing debug implementation.

winit/src/clipboard.rs

@@ -1,6 +1,12 @@
+/// A buffer for short-term storage and transfer within and between
+/// applications.
+#[allow(missing_debug_implementations)]
 pub struct Clipboard(window_clipboard::Clipboard);
 
 impl Clipboard {
+    /// Creates a new [`Clipboard`] for the given window.
+    ///
+    /// [`Clipboard`]: struct.Clipboard.html
     pub fn new(window: &winit::window::Window) -> Option<Clipboard> {
         window_clipboard::Clipboard::new(window).map(Clipboard).ok()
     }