* A bug fixes
* Sync zh and zh-hant versions.
* Fix a question in chapter_array_and_linkedlist/summary.md
* Optimize a definition in what_is_dsa.md
* Fix the Contributing guidelines for Chinese-to-English.
* Add a q&a in chapter_array_and_linkedlist/summary.md
* Sync zh and zh-hant versions.
* Update .gitignore
* Sync zh and zh-hant versions.