* 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.
* Revised the figures thoughout the book.
* Utilize roboto and roboto mono as the font faimly of the English edition
* Fix the naming style
* Update two figures.
* Fix margin of the hero image
* Fix margin of the hero image
* Update all the figures
* Update the data structure, sorting, divide and conquer chapters' covers. Add the English edition covers.
* Fix the link of EN translation in README
* Update README.md
* Update README.md
* Update README-en.md