Add insert to left thumb key in NAV layer on Zaphod Lite.

This makes dedicated shift unavailable in the nav layer, but the
sticky one is there on the right hand, and there had been no binding
for insert at all before.

config/zaphod_lite.keymap

@@ -167,12 +167,12 @@ keymap {
 // | ^Q  | ^W  | ^E  | ^R  | ^T  |   | Home| PgD |  Up | PgU | Bks |
 // | ^A  | ^S  | ^D  | ^F  | ^G  |   | End | Left| Down|Right| Ret |
 // | ^Z  | ^X  | ^C  | ^V  | Del |   | GUI | Ctrl|Shift| Alt | Tab |
-// `-----------------|Layer|     |   |Base |SymLk|-----------------'
+// `-----------------|Layer| Ins |   |Base |SymLk|-----------------'
     bindings = <
 &kp LC(Q) &kp LC(W) &kp LC(E) &kp LC(R) &kp LC(T)   &kp HOME &kp PG_DN &kp UP     &kp PG_UP &kp BSPC
 &kp LC(A) &kp LC(S) &kp LC(D) &kp LC(F) &kp LC(G)   &kp END  &kp LEFT  &kp DOWN   &kp RIGHT &kp RET
 &kp LC(Z) &kp LC(X) &kp LC(C) &kp LC(V) &kp DEL     &sk RGUI &sk RCTRL &sk RSHIFT &sk LALT  &kp TAB
-                                &none &trans       &tog NAV &to SYM
+                                &none &kp INS       &tog NAV &to SYM
     >;
     display-name = "NAV";
   };