* Update the contributors list.
* Update the version number.
* Sync zh and zh-hant versions.
* Move epub builder to the utils branch.
* Optimize all figure files using pngquant.
* Update copyright.
* Update Acknowledgements.
* Update buttons in README.
* Update pythontutor block with the latest code
* Move docs-en to en/docs
* Move mkdocs.yml and README to en folder
* Fix en/mkdocs.yml
* Update the landing page
* Fix the glossary
* Reduce the font size of the code block tabs
* Add Kotlin blocks to en/docs
* Fix the code link in en/.../deque.md
* Fix the EN README link