Persian Translation of UI Elements (#2004)

* Add Persian translation to ui-text.yml
* Mention the added Persian translation in the documentation

docs/_pages/about.md

@@ -33,7 +33,7 @@ Minimal Mistakes is a flexible two-column Jekyll theme. Perfect for hosting your
 - Optional [header images](https://mmistakes.github.io/minimal-mistakes/docs/layouts/#headers), [custom sidebars](https://mmistakes.github.io/minimal-mistakes/docs/layouts/#sidebars), [table of contents](https://mmistakes.github.io/minimal-mistakes/docs/helpers/#table-of-contents), [galleries](https://mmistakes.github.io/minimal-mistakes/docs/helpers/#gallery), related posts, [breadcrumb links](https://mmistakes.github.io/minimal-mistakes/docs/configuration/#breadcrumb-navigation-beta), [navigation lists](https://mmistakes.github.io/minimal-mistakes/docs/helpers/#navigation-list), and more.
 - Commenting support (powered by [Disqus](https://disqus.com/), [Facebook](https://developers.facebook.com/docs/plugins/comments), Google+, [Discourse](https://www.discourse.org/), [utterances](https://utteranc.es/), static-based via [Staticman v1 and v2](https://staticman.net/), and custom).
 - [Google Analytics](https://www.google.com/analytics/) support.
-- UI localized text in English (default), Brazilian Portuguese (Português brasileiro), Chinese, Danish, Dutch, French (Français), German (Deutsch), Greek, Hindi (हिंदी), Hungarian, Indonesian, Italian (Italiano), Japanese, Korean, Nepali (Nepalese), Polish, Punjabi (ਪੰਜਾਬੀ), Romanian, Russian, Slovak, Spanish (Español), Swedish, Turkish (Türkçe), and Vietnamese.
+- UI localized text in English (default), Brazilian Portuguese (Português brasileiro), Chinese, Danish, Dutch, French (Français), German (Deutsch), Greek, Hindi (हिंदी), Hungarian, Indonesian, Italian (Italiano), Japanese, Korean, Nepali (Nepalese), Persian (فارسی), Polish, Punjabi (ਪੰਜਾਬੀ), Romanian, Russian, Slovak, Spanish (Español), Swedish, Turkish (Türkçe), and Vietnamese.
 
 ## Demo Pages