Mixed RTL text support

[alirezaalavi87]

Summary

Hi. I want to use Persian alongside english in our boards. this feature can be easily implemented by adding dir="auto" to some of the elements such as : input.Editable & .MarkdownEditor

so by doing that , a text like this will no longer create an issue:
یک دو test rtl تست

How important this is to me and why

Importance: High

Use cases:

1. Almost all RTL language users, specially in the technical fields, use a mix of two languages to refer to technical terms or even numbers. so this feature is a must for them.

[alirezaalavi87]

As we can see, this is a standard. ( try inspecting my initial issue comment and you will see there is dir="auto" in github too.

I am willing to do the needed changes myself.