Implemented power management (#67)

- Implemented HAL for for power management
- Implemented the Power app (accessible via Settings app)
- Implemented status bar icon for battery status

boards/waveshare_s3_touch/waveshare_s3_touch.c

@@ -9,5 +9,7 @@ const HardwareConfig waveshare_s3_touch = {
     .display = {
         .set_backlight_duty = NULL // TODO: This requires implementing the CH422G IO expander
     },
-    .init_graphics = &ws3t_init_lvgl
+    .init_graphics = &ws3t_init_lvgl,
+    .sdcard = NULL,
+    .power = NULL
 };