Implement methods to go backwards and look backwards inside Scanner

Is your feature request related to a problem? Please describe.
I'm trying to implement an InlineContentParser for images from a custom markdown spec from a certain website. Given I already parsed the opener, the spec requires me to look for the first whitespace character or end of text, then going backwards from there, look for the first ). Everything between the opener and ) is considered the image link.

This is a bit annoying to implement with the current limited set of methods Scanner has, and I also imagine the performance would be worse when instead of going backwards from the closer, you go forward from the opener via scanner.find(')') and perform an additional find to see if you just found the last ).

Describe the solution you'd like
I would like for there to be similar methods to next and find that would instead look back from the current Scanner position, i.e prev, and findPrev. Then I could just do the following (sorry that the code is in Kotlin as I don't regularly write Java, I hope the intent is clear):

val start = scanner.position()  // position after the opener has been parsed
scanner.find { char -> char.isWhitespace() } // scanner gets moved to first whitespace or very end if there is none
scanner.findPrev(')') // scanner gets moved backwards until the position is at ')'. Ideally there would also be an overload that takes a position until which it should move, so i could pass the `start` to it and it would early exit if it doesn't find one by then
val end = scanner.position() 
val imageLink = scanner.getSource(start, end).getContent()

Describe alternatives you've considered
As stated above I have considered iterating forward from the current position to find the next ) and check if there's another one to see if I'd found the last one.

Scanner のエントリーポイントから始め、issue に記載されている既存の next と find の動作を比較します。要求どおりに scanner の位置を更新する後方相当の機能を、範囲を限定した検索動作を含めて定義し、image-link のパースのユースケースで期待される範囲を取得できることを検証します。