Support JPEG comment markers in MJPEG encoder (#219)

* Skip JPEG comments

* simplify code

---------

Co-authored-by: Alessandro Ros <aler9.dev@gmail.com>

pkg/codecs/jpeg/jpeg.go

@@ -10,4 +10,5 @@ const (
 	MarkerStartOfFrame1           = 0xC0
 	MarkerStartOfScan             = 0xDA
 	MarkerEndOfImage              = 0xD9
+	MarkerComment                 = 0xFE
 )

pkg/formatdecenc/rtpmjpeg/encoder.go

@@ -95,7 +95,8 @@ outer:
 
 		switch h1 {
 		case 0xE0, 0xE1, 0xE2, // JFIF
-			jpeg.MarkerDefineHuffmanTable:
+			jpeg.MarkerDefineHuffmanTable,
+			jpeg.MarkerComment:
 			mlen := int(image[0])<<8 | int(image[1])
 			if len(image) < mlen {
 				return nil, fmt.Errorf("image is too short")