README.ijg: Clarification regarding JPEG 2000/XR

The sentence:
"Indeed, one of the original reasons for developing this free software
was to help force convergence on common, interoperable format standards
for JPEG files."
might be seen to imply that JPEG 2000 and JPEG XR are not interoperable
with themselves, although it is certainly the case that those formats
are not interoperable with each other, nor with
ITU T.81 | ISO/IEC 10918.  They are also certainly not as common as
ITU T.81 | ISO/IEC 10918, and (as an example) popular web browsers will
not display JPEG 2000 files.

The sentence in question was originally referring to proprietary,
non-standard formats and was meant to provide historical context.
libjpeg was originally released prior to the adoption of JFIF as an
official standard, so it encouraged adoption of JFIF as a de facto
standard by providing, under a business-friendly free software license,
a library for reading and writing images in that format.

README.ijg

@@ -263,7 +263,7 @@ a subset thereof, but there are other formats containing the name "JPEG" that
 are incompatible with the DCT-based JPEG standard or with JFIF (for instance,
 JPEG 2000 and JPEG XR).  This software therefore does not support these
 formats.  Indeed, one of the original reasons for developing this free software
-was to help force convergence on common, interoperable format standards for
+was to help force convergence on a common, interoperable format standard for
 JPEG files.
 
 JFIF is a minimal or "low end" representation.  TIFF/JPEG (TIFF revision 6.0 as