Add prev/next mouse buttons

KeyboardioHID already supports these keys, so lets expose them!

Fixes #28.

Signed-off-by: Gergely Nagy <algernon@keyboard.io>

README.md

@@ -85,8 +85,9 @@ properties (see below).
 Buttons are even simpler than movement: there is no movement speed, nor
 acceleration involved. One just presses them.
 
-* `Key_mouseBtnL`, `Key_mouseBtnM`, `Key_mouseBtnR`: The left, middle, and right
+* `Key_mouseBtnL`, `Key_mouseBtnM`, `Key_mouseBtnR`, `Key_mouseBtnP`,
-  mouse buttons, respectively.
+  `Key_mouseBtnN`: The left, middle, right, previous, and next mouse buttons,
+  respectively.
 
 ## Warping
 

src/MouseKeyDefs.h

@@ -22,7 +22,8 @@
 #define KEY_MOUSE_BTN_L MOUSE_LEFT // Synthetic key
 #define KEY_MOUSE_BTN_M MOUSE_MIDDLE  // Synthetic key
 #define KEY_MOUSE_BTN_R MOUSE_RIGHT  // Synthetic key
-
+#define KEY_MOUSE_BTN_P MOUSE_PREV
+#define KEY_MOUSE_BTN_N MOUSE_NEXT
 
 #define KEY_MOUSE_UP            B0000001
 #define KEY_MOUSE_DOWN          B0000010
@@ -62,3 +63,5 @@
 #define Key_mouseBtnL     (Key) { KEY_MOUSE_BUTTON | KEY_MOUSE_BTN_L, KEY_FLAGS | SYNTHETIC | IS_MOUSE_KEY }
 #define Key_mouseBtnM     (Key) { KEY_MOUSE_BUTTON | KEY_MOUSE_BTN_M, KEY_FLAGS | SYNTHETIC | IS_MOUSE_KEY }
 #define Key_mouseBtnR     (Key) { KEY_MOUSE_BUTTON | KEY_MOUSE_BTN_R, KEY_FLAGS | SYNTHETIC | IS_MOUSE_KEY }
+#define Key_mouseBtnP     (Key) { KEY_MOUSE_BUTTON | KEY_MOUSE_BTN_P, KEY_FLAGS | SYNTHETIC | IS_MOUSE_KEY }
+#define Key_mouseBtnN     (Key) { KEY_MOUSE_BUTTON | KEY_MOUSE_BTN_N, KEY_FLAGS | SYNTHETIC | IS_MOUSE_KEY }