* 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
* translation update: Update summary.md
added and refined some parts.
I feel like that this chapter is already pretty well translated.
* translation: Update summary.md
rewritten some parts of the sentence as per Thomas suggested.
please note that some parts I re-wrote it a bit differently.
* translation update: summary.md
Added what Ymmma suggested
* translation: Update index.md
refined some parts of the sentences.
changed 'in' to 'on' as it conveys a sense of movement along a path
* translation: Update index.md
changed some words per Thomas's suggestions.
* 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
