* Sync zh and zh-hant versions.
* Remove the polyfill.io link from mkdocs.yml
* Update contributors' info for code reviewers and en/zh-hant versions reviewers.
* Fix graph.md
* Update avatars for English version reviewers.
* Sync zh and zh-hant versions.
* Fix two_sum_brute_force.png
* Sync zh and zh-hant versions.
Optimize structrue of index.html.
* Format index.html
* Update bucket_sort.c
* Fix the comments in quick_sort.c
* Update the announce badge
* Sync zh and zh-hant versions
* Update contributors list.
* Sync zh and zh-hant versions.
* Sync zh and zh-hant versions.
* Update the contributors list
* Update the version number