Make it clear that the best quality is lossless

Define AVIF_QUALITY_LOSSLESS right after AVIF_QUALITY_BEST to make it
clear that AVIF_QUALITY_LOSSLESS is the same as AVIF_QUALITY_BEST.

Author: wantehchang

include/avif/avif.h

@@ -101,9 +101,9 @@ typedef int avifBool;
 #define AVIF_DEFAULT_IMAGE_COUNT_LIMIT (12 * 3600 * 60)
 
 #define AVIF_QUALITY_DEFAULT -1
-#define AVIF_QUALITY_LOSSLESS 100
 #define AVIF_QUALITY_WORST 0
 #define AVIF_QUALITY_BEST 100
+#define AVIF_QUALITY_LOSSLESS 100
 
 #define AVIF_QUANTIZER_LOSSLESS 0
 #define AVIF_QUANTIZER_BEST_QUALITY 0