Initial dutch translation (#561)

* Dutch translations for CONTRIBUTING.

* Dutch translations for README.

* Can't believe I forgot the title :)

* Alphabetize language listings.

* Use a less literal translation.

* Use arabic comma

* remove comma

* use arabic comma

* use arabic comma

* Add Software Hertigate badge

* Translate dates to Dutch.

* Translate names of functions.

Co-authored-by: James Harris <wopian@wopian.me>

CONTRIBUTING.zh_cn.md

@@ -2,6 +2,7 @@
 
 :crossed_flags:
 [English][EN],
+[Nederlands][NL],
 [العربية][AR],
 [한국어][KO_KR],
 中文
@@ -10,6 +11,7 @@
 [AR]:CONTRIBUTING.ar.md
 [KO_KR]:CONTRIBUTING.ko_kr.md
 [ZH_CN]:CONTRIBUTING.zh_cn.md
+[NL]:CONTRIBUTING.nl.md
 
 本仓库中的源代码来自对纸质打印输出文件的手动数字化，所以会不小心引入一些拼写错误和其他差异。这些代码应该被修正以使其与原纸质打印输出文件内容保持一致：