Add Arabic README and CONTRIBUTING (#404)

* Add Arabic translation for README and CONTRIBUTING

* Move Arabic to alphabetical location in CONTRIBUTING

* Update CONTRIBUTING.ko_kr.md

* Update CONTRIBUTING.md

* Update README.zh_tw.md

* Update README.zh_cn.md

* Update README.zh_cn.md

* Update README.ru.md

* Update README.pt_br.md

* Update README.md

* Update README.ko_kr.md

* Update README.it.md

* Update README.id.md

* Update README.hi_in.md

* Update README.fr.md

* Update README.es.md

* Update README.de.md

* Update README.ar.md

* Update README.zh_tw.md

CONTRIBUTING.ko_kr.md

@@ -2,9 +2,11 @@
 
 :crossed_flags:
 [English][EN],
+[العربية][AR],
 한국어
 
 [EN]:CONTRIBUTING.md
+[AR]:CONTRIBUTING.ar.md
 [KO_KR]:CONTRIBUTING.ko_kr.md
 
 ## 유용한 확장기능들