web: Investigate support for input drag-and-drop

[antangelo]

It appears there is a method of obtaining FileSystem API handles off of drag-and-drop events in the browser: https://developer.mozilla.org/en-US/docs/Web/API/DataTransferItem/getAsFileSystemHandle

Investigate whether this is feasible for use to select the input file/directory in the web flows. If this is feasible, the implementation should also be able to deduce the input type from what is dropped.