feat: add Sway backend

monitor-lets-go.example.yaml

@@ -1,7 +1,7 @@
 # monitor-lets-go example configuration
 # Copy to ~/.config/monitor-lets-go/config.yaml and adjust for your hardware.
 
-# Backend selection: "auto" (recommended), "hyprland", or "sway" (future).
+# Backend selection: "auto" (recommended), "hyprland", or "sway".
 backend: auto
 
 # Quiet period after the last hotplug event before re-evaluating.
@@ -19,6 +19,7 @@ restore_on_exit: true
 # Hyprland supports:
 #   output_path — path to the generated monitor config file
 #                 (default: ~/.config/hypr/monitors.conf)
+# Sway supports no backend-specific options (uses swaymsg commands directly).
 # backend_config:
 #   output_path: ~/.config/hypr/custom-monitors.conf