[Core] Tri Layer Keys (#19795)

Co-authored-by: wilba <[email protected]>
Co-authored-by: Pablo Martínez <[email protected]>
Co-authored-by: Joel Challis <[email protected]>
Co-authored-by: Nick Brassel <[email protected]>

quantum/process_keycode/process_tri_layer.h

@@ -0,0 +1,16 @@
+// Copyright 2023 QMK
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "action.h"
+
+/**
+ * @brief Handles tri layer behavior
+ *
+ * @param keycode the keycode
+ * @param record the key record structure
+ * @return true continue handling keycodes
+ * @return false stop handling keycodes
+ */
+bool process_tri_layer(uint16_t keycode, keyrecord_t *record);