Adds screenshot bindings to f10

On my new laptop, I have decided to keep the f keys as f keys which
requires hitting the fn key to get additional functions such as
play/pause etc. I did this because I often found myself hitting mute
(for example) by mistake. However, I don't use f10 for anything else so
rather than pushing fn+f10 (prt sc on my keyboard), I just want to push
f10. The shift / ctrl modifiers were implemented.

config.def.h

@@ -172,6 +172,9 @@ static Key keys[] = {
 	{ 0,                            XK_Print,                  0,         spawn,          {.v = fullscreenshot } },
 	{ ControlMask,                  XK_Print,                  0,         spawn,          {.v = activescreenshot } },
 	{ ShiftMask,                    XK_Print,                  0,         spawn,          {.v = selectscreenshot } },
+	{ 0,                            XK_F10,                    0,         spawn,          {.v = fullscreenshot } },
+	{ ControlMask,                  XK_F10,                    0,         spawn,          {.v = activescreenshot } },
+	{ ShiftMask,                    XK_F10,                    0,         spawn,          {.v = selectscreenshot } },
 	{ 0,                            XF86XK_AudioPlay,          0,         spawn,          {.v = playpause } },
 	{ 0,                            XF86XK_AudioPause,         0,         spawn,          {.v = playpause } },
 	{ MODKEY|ShiftMask,             XK_d,                      0,         spawn,          {.v = date } },