Support for files without a file extension (via "File type auto-detected by file content")

[codebymikey]

Sometimes a bunch of files might be available on disk (e.g. gzipped/non-gzipped HTTP responses) without a consistent consistent extension type - In my situation, a response from scrapy.

It'd be nice if we could integrate with the "File type auto-detected by file content" file type by presumably checking the header bytes of the file content:

Even manually assigning it to the Archiver content type doesn't allow it to be detected without explicitly renaming the file.