Implement new Go based Desktop app

This focuses on Windows first, but coudl be used for Mac
and possibly linux in the future.

app/tray/wintray/notifyicon.go

@@ -0,0 +1,66 @@
+//go:build windows
+
+package wintray
+
+import (
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+// Contains information that the system needs to display notifications in the notification area.
+// Used by Shell_NotifyIcon.
+// https://msdn.microsoft.com/en-us/library/windows/desktop/bb773352(v=vs.85).aspx
+// https://msdn.microsoft.com/en-us/library/windows/desktop/bb762159
+type notifyIconData struct {
+	Size                       uint32
+	Wnd                        windows.Handle
+	ID, Flags, CallbackMessage uint32
+	Icon                       windows.Handle
+	Tip                        [128]uint16
+	State, StateMask           uint32
+	Info                       [256]uint16
+	// Timeout, Version           uint32
+	Timeout uint32
+
+	InfoTitle   [64]uint16
+	InfoFlags   uint32
+	GuidItem    windows.GUID
+	BalloonIcon windows.Handle
+}
+
+func (nid *notifyIconData) add() error {
+	const NIM_ADD = 0x00000000
+	res, _, err := pShellNotifyIcon.Call(
+		uintptr(NIM_ADD),
+		uintptr(unsafe.Pointer(nid)),
+	)
+	if res == 0 {
+		return err
+	}
+	return nil
+}
+
+func (nid *notifyIconData) modify() error {
+	const NIM_MODIFY = 0x00000001
+	res, _, err := pShellNotifyIcon.Call(
+		uintptr(NIM_MODIFY),
+		uintptr(unsafe.Pointer(nid)),
+	)
+	if res == 0 {
+		return err
+	}
+	return nil
+}
+
+func (nid *notifyIconData) delete() error {
+	const NIM_DELETE = 0x00000002
+	res, _, err := pShellNotifyIcon.Call(
+		uintptr(NIM_DELETE),
+		uintptr(unsafe.Pointer(nid)),
+	)
+	if res == 0 {
+		return err
+	}
+	return nil
+}