Expose API similar to for_each_entries but without callback

[judemille]

For my use-case, I need to get a stream to a file within the archive, without deferring to a callback. I don't mind this action blocking all other use of the archive until that file handle is closed. The main issue is just that I cannot work with a callback.

[dyz1990]

@judemille Can you provide an example of using this API?

[judemille]

Something along the lines of

let mut file: FileReader = archive.get_file_at_path("file.dsf");
// FileReader is Read + Seek.

would be ideal.