Add more compressed file types to the list of file types that krarc supports
In the krarc.protocol file it's stated that krarc supports some types of files, although the list is not complete. For example, it supports .7z files.
Note: krarc is supposed to open filetypes like .arj or .lha, although they are practically unused.
Differential Revision: https://phabricator.kde.org/D23276