It's 2026 and things like kashida in CSS is not possible. Long way to go to support the Arabic script properly on the web.
And as the article says, since most of the writing is happening on computers, stuff like kashida are going to be forgotten soon.
Hmm. by kashida do you mean something like 'ایـــــــــــــن'?
I don't think you mean this, because I don't know how would you do it in CSS. Looks more like a problem to be solved with different types of character than styling.
You may want to explain more.