Add copyright for the word2vec (#5063)

* Add the copyright for the word-embedding

* add the the link for the chinese word embedding

PaddleNLP/examples/word_embedding/README.md

@@ -93,3 +93,6 @@ Eval Acc：
 | ------------------------------------| -------------  |
 | paddle.nn.Embedding                 |    0.8965      |
 | paddelnlp.embeddings.TokenEmbedding |    0.9082      |
+
+## 致谢
+- 感谢 [Chinese-Word-Vectors](https://github.com/Embedding/Chinese-Word-Vectors)提供Word2Vec中文Embedding来源。

PaddleNLP/paddlenlp/embeddings/constant.py

-# Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
+# Copyright (c) 2020 PaddlePaddle Authors and Chinese-Word-Vectors Authors. All Rights Reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.