Add Persian translation link (#115)

README.md

-*[English](README.md) ∙ [简体中文](README-zh-Hans.md) | [Brazilian Portuguese](https://github.com/donnemartin/system-design-primer/issues/40) ∙ [Italian](https://github.com/donnemartin/system-design-primer/issues/104) ∙ [Japanese](https://github.com/donnemartin/system-design-primer/issues/100) ∙ [Korean](https://github.com/donnemartin/system-design-primer/issues/102) ∙ [Polish](https://github.com/donnemartin/system-design-primer/issues/68) ∙ [Russian](https://github.com/donnemartin/system-design-primer/issues/87) ∙ [Traditional Chinese](https://github.com/donnemartin/system-design-primer/issues/88) ∙ [Turkish](https://github.com/donnemartin/system-design-primer/issues/39) | [Add Translation](https://github.com/donnemartin/system-design-primer/issues/28)*
+*[English](README.md) ∙ [简体中文](README-zh-Hans.md) | [Brazilian Portuguese](https://github.com/donnemartin/system-design-primer/issues/40) ∙ [Italian](https://github.com/donnemartin/system-design-primer/issues/104) ∙ [Japanese](https://github.com/donnemartin/system-design-primer/issues/100) ∙ [Korean](https://github.com/donnemartin/system-design-primer/issues/102) ∙ [Persian](https://github.com/donnemartin/system-design-primer/issues/110) ∙ [Polish](https://github.com/donnemartin/system-design-primer/issues/68) ∙ [Russian](https://github.com/donnemartin/system-design-primer/issues/87) ∙ [Traditional Chinese](https://github.com/donnemartin/system-design-primer/issues/88) ∙ [Turkish](https://github.com/donnemartin/system-design-primer/issues/39) | [Add Translation](https://github.com/donnemartin/system-design-primer/issues/28)*
 
 # The System Design Primer