Add Window::is_minimized

Co-authored-by: Kirill Chibisov <contact@kchibisov.com>
Co-authored-by: Markus Siglreithmaier <m.siglreith@gmail.com>

src/platform_impl/orbital/window.rs

@@ -276,6 +276,11 @@ impl Window {
     #[inline]
     pub fn set_minimized(&self, _minimized: bool) {}
 
+    #[inline]
+    pub fn is_minimized(&self) -> Option<bool> {
+        None
+    }
+
     #[inline]
     pub fn set_maximized(&self, _maximized: bool) {}