Bump the API version

Due to the plugin API redesign, plugins that migrate may want to ensure they are
compiled against a recent enough Kaleidoscope. Others may opt to provide
separate implementations for each version. For this to work, we need to bump the
API version.

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

src/Kaleidoscope.h

@@ -47,7 +47,7 @@ extern HARDWARE_IMPLEMENTATION KeyboardHardware;
  * the API is used - it is entirely up to the plugin or sketch author. The point
  * of this macro is to let them easily check the version.
  */
-#define KALEIDOSCOPE_API_VERSION 1
+#define KALEIDOSCOPE_API_VERSION 2
 
 /** Required Kaleidoscope major version.
  *