Use aether theme

Summary:
The capacity aether layout is not perfect, because of some limitation in capacity.

But this website needs to move away from capacity or the content needs to be moved to the community wiki anyway. So just a temporary fix ;)

Test Plan:

Reviewers: mpyne, kdesrc-build

Reviewed By: mpyne, kdesrc-build

Differential Revision: https://phabricator.kde.org/D23226