Since this is a tool that people should use to build upon, we should have better docblocks to describe more advanced usages of API's.

Plus, I LOVE ASCII art.

How can I include special characters in my mention?
The mention format I want is as follows:
@한글(Hangle) 입니다.
I want to know how.

The distance in points between the bottom of one line fragment and the top of the next.

https://developer.apple.com/documentation/uikit/nsmutableparagraphstyle/1528742-linespacing

writingDirection这里原文[https://developer.apple.com/documentation/foundation/nsattributedstring/key/1524497-writingdirection]描述：

The value of this attribute is an NSArray object containing NSNumber objects representing the nested levels of writing direction overrides, in order from outermost to innermost.

这里应该是一个NSNumber的数组，代码修改如下：

let dict = [NSAttributedStringKey.writingDirection:[index]]