* Add "reference" for EN version. Bug fixes.
* Unify the figure reference as "the figure below" and "the figure above".
Bug fixes.
* Format the EN markdown files.
* Replace "" with <u></u> for EN version and bug fixes
* Fix biary_tree_dfs.png
* Fix biary_tree_dfs.png
* Fix zh-hant/biary_tree_dfs.png
* Fix heap_sort_step1.png
* Sync zh and zh-hant versions.
* Bug fixes
* Fix EN figures
* Bug fixes
* Fix the figure labels for EN version
* Add Ruby and Kotlin icons
Add the avatar of @curtishd
* Update README
* Synchronize zh-hant and zh versions.
* Translate the pythontutor blocks to traditional Chinese
* Fix en/mkdocs.yml
* Update the landing page of the en version.
* Fix the Dockerfile
* Refine the en landingpage
* Fix en landing page
* Reset the README.md