Update Readme

Signed-off-by: Jael Gu <mengjia.gu@zilliz.com>

README.md

@@ -1,5 +1,9 @@
 # ElasticSearch Index
 
+author: Jael
+
+<br />
+
 ## Description
 
 The index operator index the given documents in ElasticSearch to get ready for retrieval.
@@ -7,6 +11,8 @@ It accepts a single document in dictionary or a list of documents (dictionaries)
 For each document, the index automatically generates a unique id.
 To use this operator, you need to [set up ElasticSearch](https://www.elastic.co/guide/en/elasticsearch/reference/current/setup.html) in advance.
 
+<br />
+
 ## Code Example
 
 Insert an example document into ElasticSearch with address of localhost:9200 and index of 'test_index'.
@@ -35,3 +41,36 @@ res = es_insert(example_doc) # OR: es_insert([example_doc])
 DataCollection(res).show() # Optional: display output data
 ```
 
+<br />
+
+## Factory Constructor
+
+Create the operator via the following factory method:
+
+***elasticsearch.search(host='localhost', port=9200, index_name='test_index', user=None, password=None, ca_certs=None)***
+
+**Parameters:**
+
+***host***: *str*
+
+The host to connect ElasticSearch client.
+
+***port***: *int*
+
+The port to connect ElasticSearch client.
+
+***user***: *str*
+
+The username to connect ElasticSearch client if needed, defaults to None.
+
+***password***: *str*
+
+The user password to connect ElasticSearch client if needed, defaults to None.
+
+***ca_certs***: *str*
+
+The path to CA certificates to connect ElasticSearch client if needed, defaults to None.
+
+**Returns:**
+
+Index response wrapped by `elastic_transport.ObjectApiResponse`.