Update DESIGN.md (#1478)

* Update DESIGN.md
Signed-off-by: NLutkin Wang <lu.wang@zilliz.com>

* Fix Markdown format
Signed-off-by: NJinHai-CN <hai.jin@zilliz.com>
Co-authored-by: NJin Hai <hai.jin@zilliz.com>

DESIGN.md

@@ -4,6 +4,7 @@ If you would like to propose a new feature for Milvus, it is recommended that yo
 
 The following list contains existing design documents for Milvus.
 
-- [Support DSL interface](https://docs.google.com/document/d/1U83LY36TyaG3WD67Q9HWg9saD3qQcz9BfMcEScgwQPM/edit?usp=sharing)
-- [Support delete/search by ID, attribute filtering, ID de-duplication](https://docs.google.com/document/d/1CDKdTj_DnE90YaZrPgsMaphqOTkMdbKETNrsFKj_Bco/edit?usp=sharing)
-- [Support write-ahead logging](https://docs.google.com/document/d/12N8RC_wJb2dvEKY9jrlh8hU_eH8jxQVBewoPuHNqcXE/edit?usp=sharing)
+-   [Support DSL interface](https://docs.google.com/document/d/1U83LY36TyaG3WD67Q9HWg9saD3qQcz9BfMcEScgwQPM/edit?usp=sharing)
+-   [Support delete/search by ID, attribute filtering, ID de-duplication](https://docs.google.com/document/d/1CDKdTj_DnE90YaZrPgsMaphqOTkMdbKETNrsFKj_Bco/edit?usp=sharing)
+-   [Support write-ahead logging](https://docs.google.com/document/d/12N8RC_wJb2dvEKY9jrlh8hU_eH8jxQVBewoPuHNqcXE/edit?usp=sharing)
+-   [Support in-service config modification](https://docs.google.com/document/d/1pK1joWJgAHM5nVp3q005iLbLqU5bn9InWeBy0mRAoSg/edit?usp=sharing)