feat(keymap): Add binding get/set, layer movement

* Add keymap API for getting/setting a bindings
  in keymap layers.
* Add layer move support via intemediary ordering array.
* Add settings storage for keymap changes.

app/Kconfig

@@ -258,6 +258,18 @@ rsource "src/split/Kconfig"
 #Basic Keyboard Setup
 endmenu
 
+menu "Keymaps"
+
+config ZMK_KEYMAP_LAYER_REORDERING
+    bool "Layer Reordering Support"
+
+config ZMK_KEYMAP_SETTINGS_STORAGE
+    bool "Settings Save/Load"
+    depends on SETTINGS
+    depends on ZMK_BEHAVIOR_LOCAL_IDS
+
+endmenu # Keymaps
+
 rsource "src/studio/Kconfig"
 
 menu "Display/LED Options"

app/include/zmk/keymap.h

@@ -12,17 +12,44 @@
 #define ZMK_KEYMAP_LAYERS_LEN                                                                      \
     (DT_FOREACH_CHILD(DT_INST(0, zmk_keymap), ZMK_LAYER_CHILD_LEN_PLUS_ONE) 0)
 
+typedef uint8_t zmk_keymap_layer_id_t;
+typedef uint8_t zmk_keymap_layer_index_t;
+
 typedef uint32_t zmk_keymap_layers_state_t;
 
-uint8_t zmk_keymap_layer_default(void);
+zmk_keymap_layer_id_t zmk_keymap_layer_index_to_id(zmk_keymap_layer_index_t layer_index);
+
+zmk_keymap_layer_id_t zmk_keymap_layer_default(void);
 zmk_keymap_layers_state_t zmk_keymap_layer_state(void);
-bool zmk_keymap_layer_active(uint8_t layer);
-uint8_t zmk_keymap_highest_layer_active(void);
-int zmk_keymap_layer_activate(uint8_t layer);
-int zmk_keymap_layer_deactivate(uint8_t layer);
-int zmk_keymap_layer_toggle(uint8_t layer);
-int zmk_keymap_layer_to(uint8_t layer);
-const char *zmk_keymap_layer_name(uint8_t layer);
+bool zmk_keymap_layer_active(zmk_keymap_layer_id_t layer);
+zmk_keymap_layer_id_t zmk_keymap_highest_layer_active(void);
+int zmk_keymap_layer_activate(zmk_keymap_layer_id_t layer);
+int zmk_keymap_layer_deactivate(zmk_keymap_layer_id_t layer);
+int zmk_keymap_layer_toggle(zmk_keymap_layer_id_t layer);
+int zmk_keymap_layer_to(zmk_keymap_layer_id_t layer);
+const char *zmk_keymap_layer_name(zmk_keymap_layer_id_t layer);
+
+const struct zmk_behavior_binding *zmk_keymap_get_layer_binding_at_idx(zmk_keymap_layer_id_t layer,
+                                                                       uint8_t binding_idx);
+int zmk_keymap_set_layer_binding_at_idx(zmk_keymap_layer_id_t layer, uint8_t binding_idx,
+                                        const struct zmk_behavior_binding binding);
+
+#if IS_ENABLED(CONFIG_ZMK_KEYMAP_LAYER_REORDERING)
+
+int zmk_keymap_move_layer(zmk_keymap_layer_index_t start_idx, zmk_keymap_layer_index_t dest_idx);
+
+#endif
+
+/**
+ * @brief Check if there are any unsaved keymap changes.
+ *
+ * @retval 0 if there are no changes.
+ * @retval 1 if there are changes.
+ */
+int zmk_keymap_check_unsaved_changes(void);
+
+int zmk_keymap_save_changes(void);
+int zmk_keymap_discard_changes(void);
 
 int zmk_keymap_position_state_changed(uint8_t source, uint32_t position, bool pressed,
                                       int64_t timestamp);