Major plugin updates

v3/plugins/experimental/single_instance/plugin_linux.go

@@ -0,0 +1,29 @@
+//go:build linux
+
+package single_instance
+
+import (
+	"os"
+	"os/signal"
+	"syscall"
+
+	"github.com/wailsapp/wails/v3/pkg/application"
+)
+
+func init() {
+	sigc := make(chan os.Signal, 1)
+	signal.Notify(sigc,
+		syscall.SIGUSR2,
+	)
+	go func() {
+		for {
+			<-sigc
+			application.Get().Show()
+		}
+	}()
+}
+
+func (p *Plugin) activeInstance(pid int) error {
+	syscall.Kill(pid, syscall.SIGUSR2)
+	return nil
+}