Update changelog for release

CHANGELOG.md

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 All notable changes to the Lethe project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/).
 
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+## Release of Lethe v1.0 - 2024-11-30
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+The lethe v1.0 release marks the transition of lethe to a numbered released format. Following numbered releases will be generated more often and we aim to release a numbered version 4 to 6 times per year or when sufficient changes have been realized.
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+The lethe v1.0 release comes with a structured and stable syntax. All of the examples and test provided with lethe were re-ran with this v1.0 release to ensure that all of the results provided online are up to date. This version is production-ready and has been tested and validated extensively.
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 ## [Master] - 2024-11-28
 
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