Allow clearing text box with ESC if IME composition is empty

Author: Rampastring

src/TSMapEditor/UI/IME/IMEHandler.cs

@@ -78,8 +78,16 @@ protected virtual void OnIMETextInput(char character)
 
         if (IMEFocus != null)
         {
-            TextBoxHandleChatInputCallbacks.TryGetValue(IMEFocus, out var handleChatInput);
-            handleChatInput?.Invoke(character);
+            // Handle ESC
+            if (character == 27 && CompositionEmpty)
+            {
+                IMEFocus.Text = string.Empty;
+            }
+            else
+            {
+                TextBoxHandleChatInputCallbacks.TryGetValue(IMEFocus, out var handleChatInput);
+                handleChatInput?.Invoke(character);
+            }
         }
     }