feat: add portable Windows zone manager

internal/platform/platform_other.go

@@ -0,0 +1,12 @@
+//go:build !windows
+
+package platform
+
+import (
+	"errors"
+	"github.com/stevec/fancywin/internal/config"
+)
+
+func Run(_ string, _ config.Config, _ bool) error {
+	return errors.New("the window manager can only run on Windows")
+}