Display BLAKE2 file checksums for RAR files

Summary: When creating a RAR 5.0 archive, BLAKE2sp can be used instead of CRC32 for file checksums. This diff adds an entry for BLAKE2 file checksum.

Test Plan:
Attached is a RAR 5.0 archive using BLAKE2sp file checksums.

{F6875541}

Reviewers: #ark, elvisangelaccio

Subscribers: #ark, kde-utils-devel

Tags: #ark

Differential Revision: https://phabricator.kde.org/D21637