To cache the glyphs from the opened fonts set `LV_FREETYPE_CACHE_SIZE >= 0` and then use the following macros for detailed configuration:
1.`LV_FREETYPE_CACHE_SIZE`:maximum memory(bytes) used to cache font bitmap, outline, character maps, etc. 0 means use the system default value, less than 0 means disable cache.Note: that this value does not account for managed FT_Face and FT_Size objects.
1.`LV_FREETYPE_CACHE_FT_FACES`:maximum number of opened FT_Face objects managed by this cache instance.0 means use the system default value.Only useful when LV_FREETYPE_CACHE_SIZE >= 0.
1.`LV_FREETYPE_CACHE_FT_SIZES`:maximum number of opened FT_Size objects managed by this cache instance. 0 means use the system default value.Only useful when LV_FREETYPE_CACHE_SIZE >= 0.
When you are sure that all the used fonts size will not be greater than 256, you can enable `LV_FREETYPE_SBIT_CACHE`, which is much more memory efficient for small bitmaps.
You can use `lv_ft_font_init()` to create FreeType fonts. It returns `true` to indicate success, at the same time, the `font` member of `lv_ft_info_t` will be filled with a pointer to an lvgl font, and you can use it like any lvgl font.
Font style supports bold and italic, you can use the following macro to set:
1.`FT_FONT_STYLE_NORMAL`:default style.
1.`FT_FONT_STYLE_ITALIC`:Italic style
1.`FT_FONT_STYLE_BOLD`:bold style
They can be combined.eg:`FT_FONT_STYLE_BOLD | FT_FONT_STYLE_ITALIC`.
