Add Window::set_ime_purpose

This adds a way to set the purpose for the IME input, implemented
only on Wayland for now.

src/platform_impl/windows/window.rs

@@ -71,8 +71,8 @@ use crate::{
         Fullscreen, PlatformSpecificWindowBuilderAttributes, WindowId,
     },
     window::{
-        CursorGrabMode, CursorIcon, ResizeDirection, Theme, UserAttentionType, WindowAttributes,
-        WindowButtons, WindowLevel,
+        CursorGrabMode, CursorIcon, ImePurpose, ResizeDirection, Theme, UserAttentionType,
+        WindowAttributes, WindowButtons, WindowLevel,
     },
 };
 
@@ -733,6 +733,9 @@ impl Window {
         }
     }
 
+    #[inline]
+    pub fn set_ime_purpose(&self, _purpose: ImePurpose) {}
+
     #[inline]
     pub fn request_user_attention(&self, request_type: Option<UserAttentionType>) {
         let window = self.window.clone();