fix welcome text rerender & add copyright (#2525)

packages/web/components/common/Textarea/PromptEditor/Editor.tsx

@@ -1,3 +1,11 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+
 import { useState, useRef, useTransition } from 'react';
 import { LexicalComposer } from '@lexical/react/LexicalComposer';
 import { PlainTextPlugin } from '@lexical/react/LexicalPlainTextPlugin';