Add plugin for nextcloud-login
Test Plan:
- Apply this patch and build the project.
- Build plasma-settings project to test the plugin.
- Open Accounts item. Tap Add Account button.
- Select nexcloud from options for nextcloud-login.
Reviewers: bshah, jbbgameich, rpatwal
Reviewed By: bshah
Subscribers: nicolasfella
Differential Revision: https://phabricator.kde.org/D21738