Add ~/.local/share/icons to icons search paths

Summary: We need to add ~/.local/share/icons to icons search paths in plasma-integration.

Reviewers: jriddell, broulik, davidedmundson

Reviewed By: davidedmundson

Subscribers: rkflx, davidedmundson, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D5093