Macros: A way to run the macro on keypress only

Add a `MACRODOWN` convenience macro, that will only run the given macro
when the key toggled on. It assumes that it is called from a function
with a `keyState` argument. If the key is not pressed, the macro will
evaluate to `MACRO_NONE`.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>

libraries/Keyboardio-Macros/src/MacroSteps.h

@@ -13,6 +13,7 @@ typedef uint8_t macro_t;
 
 #define MACRO_NONE 0
 #define MACRO(...) ({static const macro_t __m[] PROGMEM = { __VA_ARGS__ }; &__m[0]; })
+#define MACRODOWN(...) (key_toggled_on(keyState) ? MACRO(__VA_ARGS__) : MACRO_NONE)
 
 #define I(n)  MACRO_ACTION_STEP_INTERVAL, n
 #define W(n)  MACRO_ACTION_STEP_WAIT, n