Update mentions regex to cover diacritics

ts/quill/mentions/completion.tsx

@@ -29,7 +29,7 @@ export type MentionCompletionOptions = {
   theme: ThemeType;
 };
 
-const MENTION_REGEX = /(?:^|\W)@([-+\w]*)$/;
+const MENTION_REGEX = /(?:^|\W)@([-+\p{L}\p{M}\p{N}]+)$/u;
 
 export class MentionCompletion {
   results: ReadonlyArray<ConversationType>;

ts/test-electron/quill/mentions/completion_test.tsx

@@ -28,7 +28,6 @@ const me: ConversationType = getDefaultConversationWithUuid({
   isMe: true,
 });
 
-// TODO diacritic
 const members: Array<ConversationType> = [
   getDefaultConversationWithUuid({
     id: '555444',