Add Ctrl-Shift tap modifier

quantum/keymap_common.h

@@ -191,6 +191,7 @@ extern const uint16_t fn_actions[];
 #define SFT_T(kc) MT(0x2, kc)
 #define ALT_T(kc) MT(0x4, kc)
 #define GUI_T(kc) MT(0x8, kc)
+#define C_S_T(kc) MT(0x3, kc) // Control + Shift e.g. for gnome-terminal
 #define MEH_T(kc) MT(0x7, kc) // Meh is a less hyper version of the Hyper key -- doesn't include Win or Cmd, so just alt+shift+ctrl
 #define ALL_T(kc) MT(0xF, kc) // see http://brettterpstra.com/2012/12/08/a-useful-caps-lock-key/