Add Bitrate to Dolphin's Additional Information

Summary:
Adds Bitrate to Dolphin's Additional information columns.

BUG: 368418

Test Plan:
Tested in KDE Neon. A bitrate column can be added and shows the bitrate in kb/s:

{F3907210}

Works for audio as well as video files!

Reviewers: #dolphin, #kde_applications, broulik, aacid, dfaure, emmanuelp

Reviewed By: #dolphin, #kde_applications, emmanuelp

Subscribers: rkflx, alexeymin, anthonyfieroni

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D7763