[lvgl] base implementation (#7116)

Co-authored-by: Jesse Hills <3060199+jesserockz@users.noreply.github.com>

esphome/components/lvgl/lvgl_hal.h

@@ -0,0 +1,21 @@
+//
+// Created by Clyde Stubbs on 20/9/2023.
+//
+
+#pragma once
+
+#ifdef __cplusplus
+#define EXTERNC extern "C"
+#include <cstddef>
+namespace esphome {
+namespace lvgl {}
+}  // namespace esphome
+#else
+#define EXTERNC extern
+#include <stddef.h>
+#endif
+
+EXTERNC size_t lv_millis(void);
+EXTERNC void *lv_custom_mem_alloc(size_t size);
+EXTERNC void lv_custom_mem_free(void *ptr);
+EXTERNC void *lv_custom_mem_realloc(void *ptr, size_t size);