add icons to taskbar control buttons

backend/windows/taskbar_buttons_unsupported.go

@@ -1,9 +1,22 @@
-//go:build !windows
-
-package windows
-
-import "errors"
-
-func InitializeTaskbarButtons(hwnd uintptr, callback func(TaskbarButton)) error {
-	return errors.New("taskbar buttons unsupported")
-}
+//go:build !windows
+
+package windows
+
+import (
+	"errors"
+	"image"
+)
+
+var err = errors.New("taskbar buttons unsupported")
+
+func InitializeTaskbarButtons(hwnd uintptr, callback func(TaskbarButton)) error {
+	return err
+}
+
+func InitializeTaskbarIcons(prev, next, play, pause image.Image) error {
+	return err
+}
+
+func SetTaskbarButtonIsPlaying(isPlaying bool) error {
+	return err
+}