DOCS-10980 document dns seedlist

Author: skerschb

source/includes/options-mongo.yaml

@@ -81,8 +81,9 @@ description: |
   .. code-block:: none
 
      mongodb+srv://server.mongodb.com/?connectionTimeout=3000ms
-  
-  
+
+  .. versionadded:: 3.6
+   
 optional: true
 replacement:
   instance: ":program:`mongod` or :program:`mongos`"

source/reference/connection-string.txt

@@ -138,6 +138,8 @@ The components of this string are:
 DNS Seedlist Connection Format
 ------------------------------
 
+.. versionadded:: 3.6
+
 In addition to the standard connection format, MongoDB supports a DNS-constructed
 seedlist. Using the DNS to construct the available servers list allows more flexibility
 of deployment and the ability to change the servers in rotation without reconfiguring