added volume getter and setter

props_get.go

@@ -17,6 +17,10 @@ func IsPaused(socket string) (bool, error) {
 	return GetProperty[bool](socket, "pause")
 }
 
+func GetVolume(socket string) (float64, error) {
+	return GetProperty[float64](socket, "volume")
+}
+
 func GetFilename(socket string) (string, error) {
 	return GetProperty[string](socket, "filename")
 }

props_set.go

@@ -17,3 +17,7 @@ func SetTimePos(socket string, timePos time.Duration) error {
 func SetPercentPos(socket string, percentPos float64) error {
 	return SetProperty[float64](socket, "percent-pos", percentPos)
 }
+
+func SetVolume(socket string, volume float64) error {
+	return SetProperty[float64](socket, "volume", volume)
+}