Update KDE's Plasma Desktop to 5.18.0

Tuesday, 11 February 2020.

Plasma 5.18 LTS is out!

A brand new version of the Plasma desktop is now available. In Plasma 5.18 you
will find neat new features that make notifications clearer, settings more
streamlined and the overall look more attractive. Plasma 5.18 is easier and
more fun to use, while at the same time allowing you to be more productive when
it is time to work.

Apart from all the cool new stuff, Plasma 5.18 also comes with an LTS status.
LTS stands for "Long Term Support". This means 5.18 will be updated and
maintained by KDE contributors for the next two years (regular versions are
maintained for 4 months). If you are thinking of updating or migrating your
school, company or organization to Plasma, this version is your best bet, as
you get the most stable version of Plasma *and* all the new features too.

Announcement:

https://kde.org/announcements/plasma-5.18.0

Changelog:

https://kde.org/announcements/plasma-5.17.5-5.18.0-changelog.php