Web Assembly Local file access enhancements

Customer studies have requested better support for local file access. This ticket is tracking that activity for Web Assembly.

Issue*:* the current file access API works best for QWidgets-based apps. In general the Javascript sandbox limits local file access.

*S*o_lution**:_ _L_ooking at what the file dialog API looks like in Qt Quick, and then extending it to support WebAssembly as well.

To access files in the operating system there is the new "File System Access API".

It allows programs that run in browsers to open a file with the ability to rewrite it and access the contents of a directory.
It allows applications in the browser to have functionalities that are similar to the desktop.

Support for this API could be an interesting addition for QT Webassembly.

The API is used by Chrome/Edge, but is not supported by Firefox and Safari for privacy reasons.
You can see how it works at https://vscode.dev/
also see comments at https://www.amitmerchant.com/how-vscode-dev-interacts-with-user-local-filesystem/

References:
https://developer.mozilla.org/en-US/docs/Web/API/File_System_Access_API
https://web.dev/file-system-access/