Update the changelog

Author: DimuthuMadushan

changelog.md

@@ -6,6 +6,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ## [Unreleased]
 
+## [1.11.0] - 2023-02-21
+
 ### Added
 - [[#1586] Add Compile Time Schema Generation for Default Parameters](https://github.com/ballerina-platform/module-ballerina-graphql/pull/1586)
 - [[#3317] Add Support to Generate GraphQL Schema for Local Service Variable Declaration](https://github.com/ballerina-platform/ballerina-library/issues/3317)