Prepare next dev iteration

Update version and changelog.

Signed-off-by: thc202 <thc202@gmail.com>

CHANGELOG.md

@@ -4,6 +4,8 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
 ## [0.21.0] - 2024-04-30
 ### Changed
 - Update Selenium to version 4.20.0.
@@ -111,6 +113,7 @@ name remains the same for compatibility with previous versions.
 ## [0.3] - 2013-09-10
 ## [0.2] - 2013-07-18
 
+[Unreleased]: https://github.com/zaproxy/zest/compare/0.21.0...HEAD
 [0.21.0]: https://github.com/zaproxy/zest/compare/0.20.0...0.21.0
 [0.20.0]: https://github.com/zaproxy/zest/compare/0.19.0...0.20.0
 [0.19.0]: https://github.com/zaproxy/zest/compare/0.18.0...0.19.0

build.gradle

@@ -17,7 +17,7 @@ java {
 }
 
 group 'org.zaproxy'
-version '0.21.0'
+version '0.22.0-SNAPSHOT'
 
 application {
     mainClass.set("org.zaproxy.zest.impl.CmdLine")