* 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
* Capitalize all the headers, list headers and figure captions
* Fix the term "LRU"
* Fix the names of source code link in avl_tree.md
* Capitalize only first letter for nav trees in mkdocs.yml
* Update code comments
* Update linked_list.md
* Update linked_list.md
* 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