Fixed #77, changed NIN_SELECT to trigger the mouse click event.

[devpelux]

After a few tests I've concluded that imo the right place for NIN_SELECT is when a mouse click event is complete (at WM_LBUTTONUP).
Tested on Win10 and Win11, NIN_SELECT is triggered only when clicking the icon with the mouse left button.

The mouse right button triggers WM_CONTEXTMENU, and the enter key triggers NIN_KEYSELECT.

This fixes the problem that the context menu is always opened when clicking with the mouse #77, now it follows the same behaviour specified for the left mouse button.

fix #77