Add a .arcconfig file to use arcanist

Summary: Signed-off-by: Gustavo Carneiro <carneirodelphi@hotmail.com>

Reviewers: patrickelectric, andreagenor, tcanabrava

Reviewed By: patrickelectric, tcanabrava

Subscribers: tcanabrava, dakon, kde-utils-devel

Differential Revision: https://phabricator.kde.org/D28607