Add changelog following https://keepachangelog.com/ format (#31)

CHANGELOG.MD

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+# Changelog
+
+## v1.5.2
+
+### Security
+
+- Bump @actions/core to v1.2.6 to address deprecations raised in #30
+
+## v1.5.1
+
+### Changed
+
+- Cache kustomize by requested version spec as key
+
+## v1.5.0
+
+### Changed
+
+- Simplified asset look up
+
+## v1.4.0
+
+### Added
+
+- Adds support for semver version ranges. Example: 3.x, 3.2.x
+- Add a step in the workflow to test the action with default value
+
+## v1.2.0
+
+N/A
+
+## v1.1.0
+
+### Fixed
+
+- Support for new download path for kustomize
+
+## v1.0.0
+
+### Changed
+
+- Update metadata