Apply st-scrollback-mouse-20191024-a2c479c.diff

config.def.h

@@ -174,6 +174,8 @@ static uint forcemousemod = ShiftMask;
  */
 static MouseShortcut mshortcuts[] = {
 	/* mask                 button   function        argument       release */
+	{ ShiftMask,            Button4, kscrollup,      {.i = 1} },
+	{ ShiftMask,            Button5, kscrolldown,    {.i = 1} },
 	{ XK_ANY_MOD,           Button2, selpaste,       {.i = 0},      1 },
 	{ ShiftMask,            Button4, ttysend,        {.s = "\033[5;2~"} },
 	{ XK_ANY_MOD,           Button4, ttysend,        {.s = "\031"} },