Added Windows support to systemvolume plugin
Summary: I've added Windows support to the systemvolume plugin.
Test Plan: Move the volume sliders in the Android app
Reviewers: kdeconnect, KDE Connect, albertvaka
Reviewed By: KDE Connect, albertvaka
Subscribers: albertvaka, kdeconnect
Tags: KDE Connect, Windows
Maniphest Tasks: T10000
Differential Revision: https://phabricator.kde.org/D16936