feat(libs): add libpng decoder (#4569)

Signed-off-by: pengyiqiang <pengyiqiang@xiaomi.com>
Co-authored-by: pengyiqiang <pengyiqiang@xiaomi.com>
Co-authored-by: Gabor Kiss-Vamosi <kisvegabor@gmail.com>

src/lv_init.c

@@ -19,6 +19,7 @@
 #include "libs/tjpgd/lv_tjpgd.h"
 #include "libs/libjpeg_turbo/lv_libjpeg_turbo.h"
 #include "libs/lodepng/lv_lodepng.h"
+#include "libs/libpng/lv_libpng.h"
 #include "draw/lv_draw.h"
 #include "misc/lv_cache.h"
 #include "misc/lv_cache_builtin.h"
@@ -234,6 +235,10 @@ void lv_init(void)
     lv_lodepng_init();
 #endif
 
+#if LV_USE_LIBPNG
+    lv_libpng_init();
+#endif
+
 #if LV_USE_TJPGD
     lv_tjpgd_init();
 #endif