Summary:
Add openFile to Share Plugin and extend handler to open local file urls

Future extension: Modify the desktop file to allow Open with > Open on connected device

Depends on D16605

Test Plan: Apply Android patch. Use kdeconnect-handler file:///somefile. Check phone for reaction

Reviewers: #kde_connect, albertvaka

Reviewed By: #kde_connect, albertvaka

Subscribers: sredman, kdeconnect

Tags: #kde_connect

Maniphest Tasks: T8637

Differential Revision: https://phabricator.kde.org/D15294