Add calamares installer to desktop

etc/skel/Desktop/calamares.desktop

+#!/usr/bin/env xdg-open
+[Desktop Entry]
+Type=Application
+Version=1.0
+Name=Install Netrunner Desktop
+GenericName=Install Netrunner Desktop
+TryExec=calamares
+Exec=pkexec /usr/bin/calamares
+Comment=Calamares — System Installer
+Icon=calamares
+Terminal=false
+StartupNotify=true
+Categories=Qt;System;