Prep changelog for release

com.unity.perception/CHANGELOG.md

 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
-## [Unreleased] 
-### Added
-
-### Changed
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-### Deprecated
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-### Removed
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-### Fixed
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-### Security
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 ## [0.1.0] - 2020-06-24
 ### This is the first release of the _Perception_ package