DOCSP-9960: add documentation for topics.regex (#10)

* DOCSP-9960: add documentation for topics.regex

Author: Chris Cho

source/kafka-sink-properties.txt

@@ -33,11 +33,20 @@ data to sink to MongoDB. For an example configuration file, see
 
    * - topics
      - list
-     - | A list of Kafka topics for the sink connector.
+     - | A list of Kafka topics that the sink connector to watch.
        |
        | *Required*
+       | **Note:** You can only define either ``topics`` or ``topics.regex``.
        | **Accepted Values**: A comma-separated list of valid Kafka topics
 
+   * - topics.regex
+     - string
+     - | A regular expression that matches the Kafka topics that the sink connector should watch.
+       |
+       | *Required*
+       | **Note:** You can only define either ``topics`` or ``topics.regex``.
+       | **Accepted Values**: A valid regular expression
+
    * - connection.uri
      - string
      - | A :manual:`MongoDB connection URI string </reference/connection-string/#standard-connection-string-format>`.