Fix webserver readme for 0.11.0 (#3765)

* Fix WebServer README.md

Signed-off-by: fishpenguin <kun.yu@zilliz.com>

* Add changelog

Signed-off-by: fishpenguin <kun.yu@zilliz.com>

* Fix cpplint

Signed-off-by: fishpenguin <kun.yu@zilliz.com>
Signed-off-by: shengjun.li <shengjun.li@zilliz.com>