Add appstream metadata file

Summary:
BUG: 388923

KLines is missing appstream metadata (http://appstream.ubuntu.com/bionic/universe/issues/klines.html). After adding the metadata file, KLines can be available in KDE Discover and GNOME Software.

Reviewers: KDE Games, ltoscano, mak

Reviewed By: ltoscano, mak

Subscribers: aacid, mak, ltoscano, KDE Games

Differential Revision: https://phabricator.kde.org/D9864