Compressed archives now contain a single root which consists of the file or
folder being compressed. Before, the archive root contained the full relative
path form the current working directory to the compressed file or folder. This
is unintuitive in most cases and not dwim.
Reliably stripping (multiple) archive extensions (e.g. .tar.gz) is not supported
by std::filesystem::path. Dots in the regular root folder name can cause issues.
fileformats.hpp adds well-known format extensions which are used for stripping
the extension.
Note that this is not used by libarchive or xwim to determine the
filters/formats for extraction. This is done by libarchive's `bidding`.
