Fix invalid cursor when IME converting (#4450)

.changeset/fix-ime-cursor-position.md

@@ -0,0 +1,5 @@
+---
+'slate-react': patch
+---
+
+Changed so that the onKeyDown event do not fired while IME converting.

packages/slate-react/src/components/editable.tsx

@@ -912,6 +912,7 @@ export const Editable = (props: EditableProps) => {
             (event: React.KeyboardEvent<HTMLDivElement>) => {
               if (
                 !readOnly &&
+                !state.isComposing &&
                 hasEditableTarget(editor, event.target) &&
                 !isEventHandled(event, attributes.onKeyDown)
               ) {