1、refactor battery indicator

widgets/battery_indicator_private.h

@@ -0,0 +1,12 @@
+#pragma once
+#include "lvgl.h"
+#include "lvgl_private.h"
+
+struct _lv_battery_indicator_t {
+    lv_obj_t obj;
+    uint8_t percentage;
+    lv_obj_t* indicator;
+    lv_obj_t* label;
+    uint32_t label_text_color;
+    uint32_t label_bg_color;
+};