Add directory picker for wasmJs

[timo-drick]

I think it is technically possible to support the directory picker also in wasmJs target.
In theory there is this File System Access API. But it is only supported on chrome based browsers.
But there is another option using the same method which is already implemented in wasmJs openFilePicker implementation.
It is supported on all major browsers. And in my project it works.
So it is just an attribute in the input html element called webkitdirectory:
https://developer.mozilla.org/en-US/docs/Web/API/HTMLInputElement/webkitdirectory

The thing is that the dialog will than return a list of File elements. But the File does also have a additional attribute: webkitRelativePath
https://developer.mozilla.org/en-US/docs/Web/API/File/webkitRelativePath
I do have implemented a prototype for my project but for me it was fine to just have a file list. Of course for the Filekit project maybe PlatformFile directory entries needed to be created. Not sure about this. So would like to discuss.
Prototype implementation: https://github.com/timo-drick/WTF-Flight-Log/blob/main/libs/file_handling/src/webMain/kotlin/de/drick/filehandling/FileInputForm.kt

I really appreciate this project. Thank you very much for the great work.

[vinceglb]

Hi @timo-drick! Thanks a lot for your kind words!

I am very interested in improving the support of the library on web targets.

Are you interested in working on a PR for that? It could help me a lot.

[timo-drick]

Yes i can try to implement this. But i just wanted to ask first and maybe discuss the strategy a bit. Because it needs maybe some bigger changes. I am already able to get a list of all files recursively. But i am not sure how to build the directory tree structure. Because this does not exist.
I think there are maybe two different approaches.

1. Change the PlatformFile implementation that it is possible to not only use File as a constructor but also create virtual directories or s.th. like that.
2. Maybe other option could be to use the https://developer.mozilla.org/en-US/docs/Web/API/FileSystemEntry as the constructor value. Which than can be a directory or a file. Maybe this would be the cleanest solution. I have to do some tests to check if it is possible to generate this objects. But should work.