[About distro] Improve name and keywords

Summary: Now it's easier to find in a search, and its name is grammatically correct.

Test Plan: {F7092462}

Reviewers: #vdg, davidedmundson

Reviewed By: davidedmundson

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D22726