Implemented focus_window (#1944)

src/window.rs

@@ -731,6 +731,21 @@ impl Window {
         self.window.set_ime_position(position.into())
     }
 
+    /// Brings the window to the front and sets input focus. Has no effect if the window is
+    /// already in focus, minimized, or not visible.
+    ///
+    /// This method steals input focus from other applications. Do not use this method unless
+    /// you are certain that's what the user wants. Focus stealing can cause an extremely disruptive
+    /// user experience.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **iOS / Android / Web / Wayland:** Unsupported.
+    #[inline]
+    pub fn focus_window(&self) {
+        self.window.focus_window()
+    }
+
     /// Requests user attention to the window, this has no effect if the application
     /// is already focused. How requesting for user attention manifests is platform dependent,
     /// see `UserAttentionType` for details.