macOS: Suppress _glfwInputKey during preediting

During preediting, the following keys

- arrow keys
- enter key
- backspace key
- ...

should not be passed to an application.

src/cocoa_window.m

@@ -580,6 +580,7 @@ static const NSRange kEmptyRange = { NSNotFound, 0 };
     const int key = translateKey([event keyCode]);
     const int mods = translateFlags([event modifierFlags]);
 
+    if (![self hasMarkedText])
         _glfwInputKey(window, key, [event keyCode], GLFW_PRESS, mods);
 
     [self interpretKeyEvents:@[event]];