Update documentation to make combining window types clearer

src/platform_impl/linux/x11/util/hint.rs

@@ -23,6 +23,7 @@ impl From<bool> for StateOperation {
 bitflags! {
     /// X window type. Maps directly to
     /// [`_NET_WM_WINDOW_TYPE`](https://specifications.freedesktop.org/wm-spec/wm-spec-1.5.html).
+    /// Combining window types is possible with the `|` operator.
     #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
     pub struct WindowType: u32 {
         /// A desktop feature. This can include a single window containing desktop icons with the same dimensions as the