community[minor]: Add Baichuan Text Embedding Model and Baichuan Inc introduction (#16568)

- **Description:** Adding Baichuan Text Embedding Model and Baichuan Inc
introduction.

Baichuan Text Embedding ranks #1 in C-MTEB leaderboard:
https://huggingface.co/spaces/mteb/leaderboard

Co-authored-by: BaiChuanHelper <wintergyc@WinterGYCs-MacBook-Pro.local>

libs/community/tests/integration_tests/embeddings/test_baichuan.py

@@ -0,0 +1,19 @@
+"""Test Baichuan Text Embedding."""
+from langchain_community.embeddings.baichuan import BaichuanTextEmbeddings
+
+
+def test_baichuan_embedding_documents() -> None:
+    """Test Baichuan Text Embedding for documents."""
+    documents = ["今天天气不错", "今天阳光灿烂"]
+    embedding = BaichuanTextEmbeddings()
+    output = embedding.embed_documents(documents)
+    assert len(output) == 2
+    assert len(output[0]) == 1024
+
+
+def test_baichuan_embedding_query() -> None:
+    """Test Baichuan Text Embedding for query."""
+    document = "所有的小学生都会学过只因兔同笼问题。"
+    embedding = BaichuanTextEmbeddings()
+    output = embedding.embed_query(document)
+    assert len(output) == 1024