Document systemd setup

[mweirauch]

A nice example was given in this issue.

# Install dropignore to ~/.local/bin and, copy this file as ~/.config/systemd/user/dropignore.service
# (The location of Dropbox folder is ~/Dropbox, change it if necessary)
#
# Enable service:
#   systemctl --user daemon-reload
#   systemctl enable --now --user dropignore.service
#
# Make sure it works:
#   journalctl --user-unit=dropignore --follow

[Unit]
Description=Watch Dropbox folder for ignored paths
ConditionPathIsDirectory=%h/Dropbox
ConditionFileIsExecutable=%h/.local/bin/dropignore

[Service]
ExecStart=%h/.local/bin/dropignore watch %h/Dropbox
Restart=on-failure

[Install]
WantedBy=graphical.target

My personal one which I use for ~1.5 years (custom dev paths):

[Unit]
Description=dropignore

[Service]
ExecStart=%h/.cargo/bin/dropignore watch /path/to/my/dropbox

[Install]
WantedBy=default.target