Make a XDG compatible autostart

[lytex]

Problem

Currently the script is copied to $XDG_CONFIG_HOME/autostart-scripts/git-sync.sh, which is not part of the XDG Standard. As far as I know, this is an undocumented feature existing only in KDE

Likewise, to prevent git-sync from starting twice if you logout and then login, an exit script is copied to $XDG_CONFIG_HOME/plasma-workspace/shutdown/exit-git-sync.sh, which is again nonstandard

Possible solutions

• Create a user systemd service in $XDG_CONFIG_HOME/systemd/user. This would have the added benefit that we can delegate restarts with Restart=on-failure and possibly get rid of wrapper.sh (at least in a desktop environment, since I assume termux doesn't have those user systemd services), and exit-git-sync.sh which is defined in kde/install.sh I think this is the better option
• Create a desktop entry in $XDG_CONFIG_HOME/autostart/git-sync.desktop. This would have to call git-sync.sh, but I'm not sure if there is an equivalent directory to store the desktop entries than will be run on logout, or if they are terminated on logout
• If the restart is not managed by wrapper.sh, $NOTIF_START would have to be moved to git-sync.sh

[lytex]

This is solved by 7be84bf, will close it when is merged to master